X-Git-Url: https://git.tcpdump.org/libpcap/blobdiff_plain/2c961ff2248fe951e57e1453bbe2a3e388912a37..e5aebee6d80c8909048dc1ce865e9adb97d94fd7:/pcap-linux.c diff --git a/pcap-linux.c b/pcap-linux.c index 76e5700c..3daa661e 100644 --- a/pcap-linux.c +++ b/pcap-linux.c @@ -3,13 +3,13 @@ * * Copyright (c) 2000 Torsten Landschoff * Sebastian Krahmer - * + * * License: BSD - * + * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: - * + * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright @@ -19,19 +19,57 @@ * 3. The names of the authors may not be used to endorse or promote * products derived from this software without specific prior * written permission. - * + * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. */ + #ifndef lint -static const char rcsid[] = - "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.31 2000-10-12 03:53:59 guy Exp $ (LBL)"; +static const char rcsid[] _U_ = + "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.110 2004-10-19 07:06:12 guy Exp $ (LBL)"; #endif /* - * Known bugs: - * - setting promiscuous on loopback gives every packet twice + * Known problems with 2.0[.x] kernels: + * + * - The loopback device gives every packet twice; on 2.2[.x] kernels, + * if we use PF_PACKET, we can filter out the transmitted version + * of the packet by using data in the "sockaddr_ll" returned by + * "recvfrom()", but, on 2.0[.x] kernels, we have to use + * PF_INET/SOCK_PACKET, which means "recvfrom()" supplies a + * "sockaddr_pkt" which doesn't give us enough information to let + * us do that. + * + * - We have to set the interface's IFF_PROMISC flag ourselves, if + * we're to run in promiscuous mode, which means we have to turn + * it off ourselves when we're done; the kernel doesn't keep track + * of how many sockets are listening promiscuously, which means + * it won't get turned off automatically when no sockets are + * listening promiscuously. We catch "pcap_close()" and, for + * interfaces we put into promiscuous mode, take them out of + * promiscuous mode - which isn't necessarily the right thing to + * do, if another socket also requested promiscuous mode between + * the time when we opened the socket and the time when we close + * the socket. + * + * - MSG_TRUNC isn't supported, so you can't specify that "recvfrom()" + * return the amount of data that you could have read, rather than + * the amount that was returned, so we can't just allocate a buffer + * whose size is the snapshot length and pass the snapshot length + * as the byte count, and also pass MSG_TRUNC, so that the return + * value tells us how long the packet was on the wire. + * + * This means that, if we want to get the actual size of the packet, + * so we can return it in the "len" field of the packet header, + * we have to read the entire packet, not just the part that fits + * within the snapshot length, and thus waste CPU time copying data + * from the kernel that our caller won't see. + * + * We have to get the actual size, and supply it in "len", because + * otherwise, the IP dissector in tcpdump, for example, will complain + * about "truncated-ip", as the packet will appear to have been + * shorter, on the wire, than the IP header said it should have been. */ @@ -40,7 +78,12 @@ static const char rcsid[] = #endif #include "pcap-int.h" +#include "sll.h" +#ifdef HAVE_DAG_API +#include "pcap-dag.h" +#endif /* HAVE_DAG_API */ + #include #include #include @@ -48,14 +91,55 @@ static const char rcsid[] = #include #include #include +#include #include #include #include -#include +#include + +/* + * If PF_PACKET is defined, we can use {SOCK_RAW,SOCK_DGRAM}/PF_PACKET + * sockets rather than SOCK_PACKET sockets. + * + * To use them, we include rather than + * ; we do so because + * + * some Linux distributions (e.g., Slackware 4.0) have 2.2 or + * later kernels and libc5, and don't provide a + * file; + * + * not all versions of glibc2 have a file + * that defines stuff needed for some of the 2.4-or-later-kernel + * features, so if the system has a 2.4 or later kernel, we + * still can't use those features. + * + * We're already including a number of other headers, and + * this code is Linux-specific (no other OS has PF_PACKET sockets as + * a raw packet capture mechanism), so it's not as if you gain any + * useful portability by using + * + * XXX - should we just include even if PF_PACKET + * isn't defined? It only defines one data structure in 2.0.x, so + * it shouldn't cause any problems. + */ +#ifdef PF_PACKET +# include + + /* + * On at least some Linux distributions (for example, Red Hat 5.2), + * there's no file, but PF_PACKET is defined if + * you include , but doesn't define + * any of the PF_PACKET stuff such as "struct sockaddr_ll" or any of + * the PACKET_xxx stuff. + * + * So we check whether PACKET_HOST is defined, and assume that we have + * PF_PACKET sockets only if it is defined. + */ +# ifdef PACKET_HOST +# define HAVE_PF_PACKET_SOCKETS +# endif /* PACKET_HOST */ +#endif /* PF_PACKET */ -#ifdef HAVE_NETPACKET_PACKET_H -#include -#endif #ifdef SO_ATTACH_FILTER #include #include @@ -66,13 +150,31 @@ typedef int socklen_t; #endif #ifndef MSG_TRUNC -#define MSG_TRUNC 0 +/* + * This is being compiled on a system that lacks MSG_TRUNC; define it + * with the value it has in the 2.2 and later kernels, so that, on + * those kernels, when we pass it in the flags argument to "recvfrom()" + * we're passing the right value and thus get the MSG_TRUNC behavior + * we want. (We don't get that behavior on 2.0[.x] kernels, because + * they didn't support MSG_TRUNC.) + */ +#define MSG_TRUNC 0x20 +#endif + +#ifndef SOL_PACKET +/* + * This is being compiled on a system that lacks SOL_PACKET; define it + * with the value it has in the 2.2 and later kernels, so that we can + * set promiscuous mode in the good modern way rather than the old + * 2.0-kernel crappy way. + */ +#define SOL_PACKET 263 #endif #define MAX_LINKHEADER_SIZE 256 -/* - * When capturing on all interfaces we use this as the buffer size. +/* + * When capturing on all interfaces we use this as the buffer size. * Should be bigger then all MTUs that occur in real life. * 64kB should be enough for now. */ @@ -81,36 +183,70 @@ typedef int socklen_t; /* * Prototypes for internal functions */ -static int map_arphrd_to_dlt(int arptype ); -static int live_open_old(pcap_t *, char *, int, int, char *); -static int live_open_new(pcap_t *, char *, int, int, char *); +static void map_arphrd_to_dlt(pcap_t *, int, int); +static int live_open_old(pcap_t *, const char *, int, int, char *); +static int live_open_new(pcap_t *, const char *, int, int, char *); +static int pcap_read_linux(pcap_t *, int, pcap_handler, u_char *); static int pcap_read_packet(pcap_t *, pcap_handler, u_char *); +static int pcap_inject_linux(pcap_t *, const void *, size_t); +static int pcap_stats_linux(pcap_t *, struct pcap_stat *); +static int pcap_setfilter_linux(pcap_t *, struct bpf_program *); +static void pcap_close_linux(pcap_t *); /* * Wrap some ioctl calls */ +#ifdef HAVE_PF_PACKET_SOCKETS static int iface_get_id(int fd, const char *device, char *ebuf); +#endif static int iface_get_mtu(int fd, const char *device, char *ebuf); static int iface_get_arptype(int fd, const char *device, char *ebuf); +#ifdef HAVE_PF_PACKET_SOCKETS static int iface_bind(int fd, int ifindex, char *ebuf); +#endif static int iface_bind_old(int fd, const char *device, char *ebuf); +#ifdef SO_ATTACH_FILTER +static int fix_program(pcap_t *handle, struct sock_fprog *fcode); +static int fix_offset(struct bpf_insn *p); +static int set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode); +static int reset_kernel_filter(pcap_t *handle); + +static struct sock_filter total_insn + = BPF_STMT(BPF_RET | BPF_K, 0); +static struct sock_fprog total_fcode + = { 1, &total_insn }; +#endif + /* - * Get a handle for a live capture from the given device. You can - * pass NULL as device to get all packages (without link level + * Get a handle for a live capture from the given device. You can + * pass NULL as device to get all packages (without link level * information of course). If you pass 1 as promisc the interface - * will be set to promiscous mode (XXX: I think this usage should + * will be set to promiscous mode (XXX: I think this usage should * be deprecated and functions be added to select that later allow * modification of that values -- Torsten). - * + * * See also pcap(3). */ pcap_t * -pcap_open_live(char *device, int snaplen, int promisc, int to_ms, char *ebuf) +pcap_open_live(const char *device, int snaplen, int promisc, int to_ms, + char *ebuf) { + pcap_t *handle; + int mtu; + int err; + int live_open_ok = 0; + struct utsname utsname; + +#ifdef HAVE_DAG_API + if (strstr(device, "dag")) { + return dag_open_live(device, snaplen, promisc, to_ms, ebuf); + } +#endif /* HAVE_DAG_API */ + /* Allocate a handle for this session. */ - - pcap_t *handle = malloc(sizeof(*handle)); + + handle = malloc(sizeof(*handle)); if (handle == NULL) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); @@ -122,15 +258,21 @@ pcap_open_live(char *device, int snaplen, int promisc, int to_ms, char *ebuf) memset(handle, 0, sizeof(*handle)); handle->snapshot = snaplen; handle->md.timeout = to_ms; - handle->md.promisc = promisc; /* - * NULL and "any" are special devices which give us the hint to + * NULL and "any" are special devices which give us the hint to * monitor all devices. */ if (!device || strcmp(device, "any") == 0) { device = NULL; handle->md.device = strdup("any"); + if (promisc) { + promisc = 0; + /* Just a warning. */ + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "Promiscuous mode not supported on the \"any\" device"); + } + } else handle->md.device = strdup(device); @@ -141,145 +283,211 @@ pcap_open_live(char *device, int snaplen, int promisc, int to_ms, char *ebuf) return NULL; } - /* - * Current Linux kernels use the protocol family PF_PACKET to - * allow direct access to all packets on the network while - * older kernels had a special socket type SOCK_PACKET to + /* + * Current Linux kernels use the protocol family PF_PACKET to + * allow direct access to all packets on the network while + * older kernels had a special socket type SOCK_PACKET to * implement this feature. * While this old implementation is kind of obsolete we need - * to be compatible with older kernels for a while so we are + * to be compatible with older kernels for a while so we are * trying both methods with the newer method preferred. */ - - if (! (live_open_new(handle, device, promisc, to_ms, ebuf) || - live_open_old(handle, device, promisc, to_ms, ebuf)) ) - { - /* + + if ((err = live_open_new(handle, device, promisc, to_ms, ebuf)) == 1) + live_open_ok = 1; + else if (err == 0) { + /* Non-fatal error; try old way */ + if (live_open_old(handle, device, promisc, to_ms, ebuf)) + live_open_ok = 1; + } + if (!live_open_ok) { + /* * Both methods to open the packet socket failed. Tidy * up and report our failure (ebuf is expected to be - * set by the functions above). + * set by the functions above). */ - free(handle->md.device); + if (handle->md.device != NULL) + free(handle->md.device); free(handle); return NULL; } - - /* - * Okay, now we have a packet stream open. Maybe we need to handle - * a timeout? In that case we set the filehandle to nonblocking - * so pcap_read can try reading the fd and call select if no data - * is available at first. - */ - if (to_ms > 0) { - int flags = fcntl(handle->fd, F_GETFL); - if (flags != -1) { - flags |= O_NONBLOCK; - flags = fcntl(handle->fd, F_SETFL, flags); - } - if (flags == -1) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, "fcntl: %s", - pcap_strerror(errno)); - pcap_close(handle); + /* + * Compute the buffer size. + * + * If we're using SOCK_PACKET, this might be a 2.0[.x] kernel, + * and might require special handling - check. + */ + if (handle->md.sock_packet && (uname(&utsname) < 0 || + strncmp(utsname.release, "2.0", 3) == 0)) { + /* + * We're using a SOCK_PACKET structure, and either + * we couldn't find out what kernel release this is, + * or it's a 2.0[.x] kernel. + * + * In the 2.0[.x] kernel, a "recvfrom()" on + * a SOCK_PACKET socket, with MSG_TRUNC set, will + * return the number of bytes read, so if we pass + * a length based on the snapshot length, it'll + * return the number of bytes from the packet + * copied to userland, not the actual length + * of the packet. + * + * This means that, for example, the IP dissector + * in tcpdump will get handed a packet length less + * than the length in the IP header, and will + * complain about "truncated-ip". + * + * So we don't bother trying to copy from the + * kernel only the bytes in which we're interested, + * but instead copy them all, just as the older + * versions of libpcap for Linux did. + * + * The buffer therefore needs to be big enough to + * hold the largest packet we can get from this + * device. Unfortunately, we can't get the MRU + * of the network; we can only get the MTU. The + * MTU may be too small, in which case a packet larger + * than the buffer size will be truncated *and* we + * won't get the actual packet size. + * + * However, if the snapshot length is larger than + * the buffer size based on the MTU, we use the + * snapshot length as the buffer size, instead; + * this means that with a sufficiently large snapshot + * length we won't artificially truncate packets + * to the MTU-based size. + * + * This mess just one of many problems with packet + * capture on 2.0[.x] kernels; you really want a + * 2.2[.x] or later kernel if you want packet capture + * to work well. + */ + mtu = iface_get_mtu(handle->fd, device, ebuf); + if (mtu == -1) { + pcap_close_linux(handle); + free(handle); return NULL; } + handle->bufsize = MAX_LINKHEADER_SIZE + mtu; + if (handle->bufsize < handle->snapshot) + handle->bufsize = handle->snapshot; + } else { + /* + * This is a 2.2[.x] or later kernel (we know that + * either because we're not using a SOCK_PACKET + * socket - PF_PACKET is supported only in 2.2 + * and later kernels - or because we checked the + * kernel version). + * + * We can safely pass "recvfrom()" a byte count + * based on the snapshot length. + */ + handle->bufsize = handle->snapshot; } + /* Allocate the buffer */ + + handle->buffer = malloc(handle->bufsize + handle->offset); + if (!handle->buffer) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "malloc: %s", pcap_strerror(errno)); + pcap_close_linux(handle); + free(handle); + return NULL; + } + + /* + * "handle->fd" is a socket, so "select()" and "poll()" + * should work on it. + */ + handle->selectable_fd = handle->fd; + + handle->read_op = pcap_read_linux; + handle->inject_op = pcap_inject_linux; + handle->setfilter_op = pcap_setfilter_linux; + handle->set_datalink_op = NULL; /* can't change data link type */ + handle->getnonblock_op = pcap_getnonblock_fd; + handle->setnonblock_op = pcap_setnonblock_fd; + handle->stats_op = pcap_stats_linux; + handle->close_op = pcap_close_linux; + return handle; } /* * Read at most max_packets from the capture stream and call the callback * for each of them. Returns the number of packets handled or -1 if an - * error occured. - * - * XXX: Can I rely on the Linux-specified behaviour of select (returning - * the time left in the timeval structure)? I really don't want to query - * the system time before each select call... - * - * pcap_read currently gets not only a packet from the kernel but also - * the sockaddr_ll returned as source of the packet. This way we can at - * some time extend tcpdump and libpcap to sniff on all devices at a time - * and find the right printing routine by using the information in the - * sockaddr_ll structure. + * error occured. */ -int -pcap_read(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user) +static int +pcap_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user) { - int status, packets; - fd_set read_fds; - struct timeval tv; - /* - * Fill in a timeval structure for select if we need to obeye a - * timeout. + * Currently, on Linux only one packet is delivered per read, + * so we don't loop. */ - if (handle->md.timeout > 0) { - tv.tv_usec = (handle->md.timeout % 1000) * 1000; - tv.tv_sec = (handle->md.timeout / 1000); - } - - /* - * Read packets until the packet limit has been reached or - * an error occured while reading. Call the user function - * for each received packet. - */ - for (packets = 0; max_packets == -1 || packets < max_packets;) - { - status = pcap_read_packet(handle, callback, user); - - if (status > 0) { - packets += status; - continue; - } else if (status == -1) - return -1; - - /* - * If no packet is available we go to sleep. FIXME: This - * might be better implemented using poll(?) - */ - FD_ZERO(&read_fds); - FD_SET(handle->fd, &read_fds); - status = select(handle->fd + 1, - &read_fds, NULL, NULL, &tv); - if (status == -1) { - snprintf(handle->errbuf, sizeof(handle->errbuf), - "select: %s", pcap_strerror(errno)); - return -1; - } else if (status == 0 || - (tv.tv_usec == 0 && tv.tv_sec == 0)) - return packets; - } - - return packets; + return pcap_read_packet(handle, callback, user); } - + /* - * Read a packet from the socket calling the handler provided by + * Read a packet from the socket calling the handler provided by * the user. Returns the number of packets received or -1 if an * error occured. */ static int pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata) { + u_char *bp; + int offset; +#ifdef HAVE_PF_PACKET_SOCKETS + struct sockaddr_ll from; + struct sll_header *hdrp; +#else struct sockaddr from; +#endif socklen_t fromlen; int packet_len, caplen; struct pcap_pkthdr pcap_header; +#ifdef HAVE_PF_PACKET_SOCKETS /* - * We don't currently use the from return value of recvfrom but - * this will probably be implemented in the future. + * If this is a cooked device, leave extra room for a + * fake packet header. */ - + if (handle->md.cooked) + offset = SLL_HDR_LEN; + else + offset = 0; +#else + /* + * This system doesn't have PF_PACKET sockets, so it doesn't + * support cooked devices. + */ + offset = 0; +#endif + /* Receive a single packet from the kernel */ + bp = handle->buffer + handle->offset; do { + /* + * Has "pcap_breakloop()" been called? + */ + if (handle->break_loop) { + /* + * Yes - clear the flag that indicates that it + * has, and return -2 as an indication that we + * were told to break out of the loop. + */ + handle->break_loop = 0; + return -2; + } fromlen = sizeof(from); - packet_len = recvfrom( - handle->fd, handle->buffer + handle->offset, - handle->snapshot, MSG_TRUNC, + packet_len = recvfrom( + handle->fd, bp + offset, + handle->bufsize - offset, MSG_TRUNC, (struct sockaddr *) &from, &fromlen); } while (packet_len == -1 && errno == EINTR); @@ -295,17 +503,91 @@ pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata) } } +#ifdef HAVE_PF_PACKET_SOCKETS + /* + * If this is from the loopback device, reject outgoing packets; + * we'll see the packet as an incoming packet as well, and + * we don't want to see it twice. + * + * We can only do this if we're using PF_PACKET; the address + * returned for SOCK_PACKET is a "sockaddr_pkt" which lacks + * the relevant packet type information. + */ + if (!handle->md.sock_packet && + from.sll_ifindex == handle->md.lo_ifindex && + from.sll_pkttype == PACKET_OUTGOING) + return 0; +#endif + +#ifdef HAVE_PF_PACKET_SOCKETS /* - * XXX: According to the kernel source we should get the real - * packet len if calling recvfrom with MSG_TRUNC set. It does + * If this is a cooked device, fill in the fake packet header. + */ + if (handle->md.cooked) { + /* + * Add the length of the fake header to the length + * of packet data we read. + */ + packet_len += SLL_HDR_LEN; + + hdrp = (struct sll_header *)bp; + + /* + * Map the PACKET_ value to a LINUX_SLL_ value; we + * want the same numerical value to be used in + * the link-layer header even if the numerical values + * for the PACKET_ #defines change, so that programs + * that look at the packet type field will always be + * able to handle DLT_LINUX_SLL captures. + */ + switch (from.sll_pkttype) { + + case PACKET_HOST: + hdrp->sll_pkttype = htons(LINUX_SLL_HOST); + break; + + case PACKET_BROADCAST: + hdrp->sll_pkttype = htons(LINUX_SLL_BROADCAST); + break; + + case PACKET_MULTICAST: + hdrp->sll_pkttype = htons(LINUX_SLL_MULTICAST); + break; + + case PACKET_OTHERHOST: + hdrp->sll_pkttype = htons(LINUX_SLL_OTHERHOST); + break; + + case PACKET_OUTGOING: + hdrp->sll_pkttype = htons(LINUX_SLL_OUTGOING); + break; + + default: + hdrp->sll_pkttype = -1; + break; + } + + hdrp->sll_hatype = htons(from.sll_hatype); + hdrp->sll_halen = htons(from.sll_halen); + memcpy(hdrp->sll_addr, from.sll_addr, + (from.sll_halen > SLL_ADDRLEN) ? + SLL_ADDRLEN : + from.sll_halen); + hdrp->sll_protocol = from.sll_protocol; + } +#endif + + /* + * XXX: According to the kernel source we should get the real + * packet len if calling recvfrom with MSG_TRUNC set. It does * not seem to work here :(, but it is supported by this code - * anyway. + * anyway. * To be honest the code RELIES on that feature so this is really * broken with 2.2.x kernels. * I spend a day to figure out what's going on and I found out - * that the following is happening: + * that the following is happening: * - * The packet comes from a random interface and the packet_rcv + * The packet comes from a random interface and the packet_rcv * hook is called with a clone of the packet. That code inserts * the packet into the receive queue of the packet socket. * If a filter is attached to that socket that filter is run @@ -315,31 +597,34 @@ pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata) * # tcpdump -d * (000) ret #68 * - * So the packet filter cuts down the packet. The recvfrom call + * So the packet filter cuts down the packet. The recvfrom call * says "hey, it's only 68 bytes, it fits into the buffer" with - * the result that we don't get the real packet length. This - * is valid at least until kernel 2.2.17pre6. + * the result that we don't get the real packet length. This + * is valid at least until kernel 2.2.17pre6. * - * tcpdump is currently fixed by changing the BPF code generator - * to not truncate the received packet. + * We currently handle this by making a copy of the filter + * program, fixing all "ret" instructions with non-zero + * operands to have an operand of 65535 so that the filter + * doesn't truncate the packet, and supplying that modified + * filter to the kernel. */ - + caplen = packet_len; if (caplen > handle->snapshot) caplen = handle->snapshot; /* Run the packet filter if not using kernel filter */ if (!handle->md.use_bpf && handle->fcode.bf_insns) { - if (bpf_filter(handle->fcode.bf_insns, handle->buffer, + if (bpf_filter(handle->fcode.bf_insns, bp, packet_len, caplen) == 0) { /* rejected by filter */ return 0; } } - + /* Fill in our own header data */ - + if (ioctl(handle->fd, SIOCGSTAMP, &pcap_header.ts) == -1) { snprintf(handle->errbuf, sizeof(handle->errbuf), "ioctl: %s", pcap_strerror(errno)); @@ -347,33 +632,222 @@ pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata) } pcap_header.caplen = caplen; pcap_header.len = packet_len; - - /* Call the user supplied callback function */ + + /* + * Count the packet. + * + * Arguably, we should count them before we check the filter, + * as on many other platforms "ps_recv" counts packets + * handed to the filter rather than packets that passed + * the filter, but if filtering is done in the kernel, we + * can't get a count of packets that passed the filter, + * and that would mean the meaning of "ps_recv" wouldn't + * be the same on all Linux systems. + * + * XXX - it's not the same on all systems in any case; + * ideally, we should have a "get the statistics" call + * that supplies more counts and indicates which of them + * it supplies, so that we supply a count of packets + * handed to the filter only on platforms where that + * information is available. + * + * We count them here even if we can get the packet count + * from the kernel, as we can only determine at run time + * whether we'll be able to get it from the kernel (if + * HAVE_TPACKET_STATS isn't defined, we can't get it from + * the kernel, but if it is defined, the library might + * have been built with a 2.4 or later kernel, but we + * might be running on a 2.2[.x] kernel without Alexey + * Kuznetzov's turbopacket patches, and thus the kernel + * might not be able to supply those statistics). We + * could, I guess, try, when opening the socket, to get + * the statistics, and if we can not increment the count + * here, but it's not clear that always incrementing + * the count is more expensive than always testing a flag + * in memory. + */ handle->md.stat.ps_recv++; - callback(userdata, &pcap_header, handle->buffer + handle->offset); + + /* Call the user supplied callback function */ + callback(userdata, &pcap_header, bp); return 1; } +static int +pcap_inject_linux(pcap_t *handle, const void *buf, size_t size) +{ + int ret; + +#ifdef HAVE_PF_PACKET_SOCKETS + if (!handle->md.sock_packet) { + /* PF_PACKET socket */ + if (handle->md.ifindex == -1) { + /* + * We don't support sending on the "any" device. + */ + strlcpy(handle->errbuf, + "Sending packets isn't supported on the \"any\" device", + PCAP_ERRBUF_SIZE); + return (-1); + } + + if (handle->md.cooked) { + /* + * We don't support sending on the "any" device. + * + * XXX - how do you send on a bound cooked-mode + * socket? + * Is a "sendto()" required there? + */ + strlcpy(handle->errbuf, + "Sending packets isn't supported in cooked mode", + PCAP_ERRBUF_SIZE); + return (-1); + } + } +#endif + + ret = send(handle->fd, buf, size, 0); + if (ret == -1) { + snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "send: %s", + pcap_strerror(errno)); + return (-1); + } + return (ret); +} + /* * Get the statistics for the given packet capture handle. - * FIXME: Currently does not report the number of dropped packets. + * Reports the number of dropped packets iff the kernel supports + * the PACKET_STATISTICS "getsockopt()" argument (2.4 and later + * kernels, and 2.2[.x] kernels with Alexey Kuznetzov's turbopacket + * patches); otherwise, that information isn't available, and we lie + * and report 0 as the count of dropped packets. */ -int -pcap_stats(pcap_t *handle, struct pcap_stat *stats) +static int +pcap_stats_linux(pcap_t *handle, struct pcap_stat *stats) { +#ifdef HAVE_TPACKET_STATS + struct tpacket_stats kstats; + socklen_t len = sizeof (struct tpacket_stats); +#endif + +#ifdef HAVE_TPACKET_STATS + /* + * Try to get the packet counts from the kernel. + */ + if (getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS, + &kstats, &len) > -1) { + /* + * In "linux/net/packet/af_packet.c", at least in the + * 2.4.9 kernel, "tp_packets" is incremented for every + * packet that passes the packet filter *and* is + * successfully queued on the socket; "tp_drops" is + * incremented for every packet dropped because there's + * not enough free space in the socket buffer. + * + * When the statistics are returned for a PACKET_STATISTICS + * "getsockopt()" call, "tp_drops" is added to "tp_packets", + * so that "tp_packets" counts all packets handed to + * the PF_PACKET socket, including packets dropped because + * there wasn't room on the socket buffer - but not + * including packets that didn't pass the filter. + * + * In the BSD BPF, the count of received packets is + * incremented for every packet handed to BPF, regardless + * of whether it passed the filter. + * + * We can't make "pcap_stats()" work the same on both + * platforms, but the best approximation is to return + * "tp_packets" as the count of packets and "tp_drops" + * as the count of drops. + * + * Keep a running total because each call to + * getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS, .... + * resets the counters to zero. + */ + handle->md.stat.ps_recv += kstats.tp_packets; + handle->md.stat.ps_drop += kstats.tp_drops; + } + else + { + /* + * If the error was EOPNOTSUPP, fall through, so that + * if you build the library on a system with + * "struct tpacket_stats" and run it on a system + * that doesn't, it works as it does if the library + * is built on a system without "struct tpacket_stats". + */ + if (errno != EOPNOTSUPP) { + snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, + "pcap_stats: %s", pcap_strerror(errno)); + return -1; + } + } +#endif + /* + * On systems where the PACKET_STATISTICS "getsockopt()" argument + * is supported on PF_PACKET sockets: + * + * "ps_recv" counts only packets that *passed* the filter, + * not packets that didn't pass the filter. This includes + * packets later dropped because we ran out of buffer space. + * + * "ps_drop" counts packets dropped because we ran out of + * buffer space. It doesn't count packets dropped by the + * interface driver. It counts only packets that passed + * the filter. + * + * Both statistics include packets not yet read from the + * kernel by libpcap, and thus not yet seen by the application. + * + * On systems where the PACKET_STATISTICS "getsockopt()" argument + * is not supported on PF_PACKET sockets: + * + * "ps_recv" counts only packets that *passed* the filter, + * not packets that didn't pass the filter. It does not + * count packets dropped because we ran out of buffer + * space. + * + * "ps_drop" is not supported. + * + * "ps_recv" doesn't include packets not yet read from + * the kernel by libpcap. + */ *stats = handle->md.stat; return 0; } /* - * Attach the given BPF code to the packet capture device. + * Description string for the "any" device. */ +static const char any_descr[] = "Pseudo-device that captures on all interfaces"; + int -pcap_setfilter(pcap_t *handle, struct bpf_program *filter) +pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf) +{ + if (pcap_add_if(alldevsp, "any", 0, any_descr, errbuf) < 0) + return (-1); + +#ifdef HAVE_DAG_API + if (dag_platform_finddevs(alldevsp, errbuf) < 0) + return (-1); +#endif /* HAVE_DAG_API */ + + return (0); +} + +/* + * Attach the given BPF code to the packet capture device. + */ +static int +pcap_setfilter_linux(pcap_t *handle, struct bpf_program *filter) { #ifdef SO_ATTACH_FILTER struct sock_fprog fcode; + int can_filter_in_kernel; + int err = 0; #endif if (!handle) @@ -384,114 +858,403 @@ pcap_setfilter(pcap_t *handle, struct bpf_program *filter) return -1; } - /* Free old filter code if existing */ - - handle->fcode.bf_len = 0; - if (handle->fcode.bf_insns) { - free(handle->fcode.bf_insns); - handle->fcode.bf_insns = NULL; - } - - /* Make our private copy of the filter */ - handle->fcode.bf_len = filter->bf_len; - handle->fcode.bf_insns = - malloc(filter->bf_len * sizeof(*filter->bf_insns)); - if (handle->fcode.bf_insns == NULL) { - snprintf(handle->errbuf, sizeof(handle->errbuf), - "malloc: %s", pcap_strerror(errno)); + if (install_bpf_program(handle, filter) < 0) + /* install_bpf_program() filled in errbuf */ return -1; - } - memcpy(handle->fcode.bf_insns, filter->bf_insns, - filter->bf_len * sizeof(*filter->bf_insns)); - /* - * Run user level packet filter by default. Will be overriden if - * installing a kernel filter succeeds. + /* + * Run user level packet filter by default. Will be overriden if + * installing a kernel filter succeeds. */ handle->md.use_bpf = 0; /* Install kernel level filter if possible */ - -#ifdef SO_ATTACH_FILTER - /* - * Oh joy, the Linux kernel uses struct sock_fprog instead of - * struct bpf_program and of course the length field is of - * different size. Pointed out by Sebastian - */ - fcode.filter = (struct sock_filter *) handle->fcode.bf_insns; - fcode.len = filter->bf_len; +#ifdef SO_ATTACH_FILTER #ifdef USHRT_MAX - if (filter->bf_len > USHRT_MAX) { + if (handle->fcode.bf_len > USHRT_MAX) { /* - * fcode.len is an unsigned short for current kernel. - * I have yet to see BPF-Code with that much instructions - * but still it is possible. So for the sake of - * correctness I added this check. + * fcode.len is an unsigned short for current kernel. + * I have yet to see BPF-Code with that much + * instructions but still it is possible. So for the + * sake of correctness I added this check. */ - fprintf(stderr, "Warning: Filter to complex for kernel\n"); - } - else -#endif - if (setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER, - &fcode, sizeof(fcode)) == 0) - { - /* Installation succeded - using kernel filter. */ - handle->md.use_bpf = 1; - } - else + fprintf(stderr, "Warning: Filter too complex for kernel\n"); + fcode.filter = NULL; + can_filter_in_kernel = 0; + } else +#endif /* USHRT_MAX */ { - /* - * Print a warning if kernel filter available but a problem - * occured using it. + /* + * Oh joy, the Linux kernel uses struct sock_fprog instead + * of struct bpf_program and of course the length field is + * of different size. Pointed out by Sebastian + * + * Oh, and we also need to fix it up so that all "ret" + * instructions with non-zero operands have 65535 as the + * operand, and so that, if we're in cooked mode, all + * memory-reference instructions use special magic offsets + * in references to the link-layer header and assume that + * the link-layer payload begins at 0; "fix_program()" + * will do that. */ - if (errno != ENOPROTOOPT && errno != EOPNOTSUPP) { - fprintf(stderr, "Warning: Kernel filter failed: %s\n", - pcap_strerror(errno)); + switch (fix_program(handle, &fcode)) { + + case -1: + default: + /* + * Fatal error; just quit. + * (The "default" case shouldn't happen; we + * return -1 for that reason.) + */ + return -1; + + case 0: + /* + * The program performed checks that we can't make + * work in the kernel. + */ + can_filter_in_kernel = 0; + break; + + case 1: + /* + * We have a filter that'll work in the kernel. + */ + can_filter_in_kernel = 1; + break; } } -#endif + + if (can_filter_in_kernel) { + if ((err = set_kernel_filter(handle, &fcode)) == 0) + { + /* Installation succeded - using kernel filter. */ + handle->md.use_bpf = 1; + } + else if (err == -1) /* Non-fatal error */ + { + /* + * Print a warning if we weren't able to install + * the filter for a reason other than "this kernel + * isn't configured to support socket filters. + */ + if (errno != ENOPROTOOPT && errno != EOPNOTSUPP) { + fprintf(stderr, + "Warning: Kernel filter failed: %s\n", + pcap_strerror(errno)); + } + } + } + + /* + * If we're not using the kernel filter, get rid of any kernel + * filter that might've been there before, e.g. because the + * previous filter could work in the kernel, or because some other + * code attached a filter to the socket by some means other than + * calling "pcap_setfilter()". Otherwise, the kernel filter may + * filter out packets that would pass the new userland filter. + */ + if (!handle->md.use_bpf) + reset_kernel_filter(handle); + + /* + * Free up the copy of the filter that was made by "fix_program()". + */ + if (fcode.filter != NULL) + free(fcode.filter); + + if (err == -2) + /* Fatal error */ + return -1; +#endif /* SO_ATTACH_FILTER */ return 0; } /* - * Linux uses the ARP hardware type to identify the type of an - * interface. pcap uses the DLT_xxx constants for this. This - * function maps the ARPHRD_xxx constant to an appropriate - * DLT_xxx constant. - * - * Returns -1 if unable to map the type. + * Linux uses the ARP hardware type to identify the type of an + * interface. pcap uses the DLT_xxx constants for this. This + * function takes a pointer to a "pcap_t", and an ARPHRD_xxx + * constant, as arguments, and sets "handle->linktype" to the + * appropriate DLT_XXX constant and sets "handle->offset" to + * the appropriate value (to make "handle->offset" plus link-layer + * header length be a multiple of 4, so that the link-layer payload + * will be aligned on a 4-byte boundary when capturing packets). + * (If the offset isn't set here, it'll be 0; add code as appropriate + * for cases where it shouldn't be 0.) + * + * If "cooked_ok" is non-zero, we can use DLT_LINUX_SLL and capture + * in cooked mode; otherwise, we can't use cooked mode, so we have + * to pick some type that works in raw mode, or fail. + * + * Sets the link type to -1 if unable to map the type. */ -static int map_arphrd_to_dlt(int arptype) +static void map_arphrd_to_dlt(pcap_t *handle, int arptype, int cooked_ok) { switch (arptype) { + case ARPHRD_ETHER: + /* + * This is (presumably) a real Ethernet capture; give it a + * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, so + * that an application can let you choose it, in case you're + * capturing DOCSIS traffic that a Cisco Cable Modem + * Termination System is putting out onto an Ethernet (it + * doesn't put an Ethernet header onto the wire, it puts raw + * DOCSIS frames out on the wire inside the low-level + * Ethernet framing). + * + * XXX - are there any sorts of "fake Ethernet" that have + * ARPHRD_ETHER but that *shouldn't offer DLT_DOCSIS as + * a Cisco CMTS won't put traffic onto it or get traffic + * bridged onto it? ISDN is handled in "live_open_new()", + * as we fall back on cooked mode there; are there any + * others? + */ + handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2); + /* + * If that fails, just leave the list empty. + */ + if (handle->dlt_list != NULL) { + handle->dlt_list[0] = DLT_EN10MB; + handle->dlt_list[1] = DLT_DOCSIS; + handle->dlt_count = 2; + } + /* FALLTHROUGH */ + case ARPHRD_METRICOM: - case ARPHRD_LOOPBACK: return DLT_EN10MB; - case ARPHRD_EETHER: return DLT_EN3MB; - case ARPHRD_AX25: return DLT_AX25; - case ARPHRD_PRONET: return DLT_PRONET; - case ARPHRD_CHAOS: return DLT_CHAOS; - case ARPHRD_IEEE802: return DLT_IEEE802; - case ARPHRD_ARCNET: return DLT_ARCNET; - case ARPHRD_FDDI: return DLT_FDDI; + case ARPHRD_LOOPBACK: + handle->linktype = DLT_EN10MB; + handle->offset = 2; + break; + + case ARPHRD_EETHER: + handle->linktype = DLT_EN3MB; + break; + + case ARPHRD_AX25: + handle->linktype = DLT_AX25; + break; + + case ARPHRD_PRONET: + handle->linktype = DLT_PRONET; + break; + + case ARPHRD_CHAOS: + handle->linktype = DLT_CHAOS; + break; + +#ifndef ARPHRD_IEEE802_TR +#define ARPHRD_IEEE802_TR 800 /* From Linux 2.4 */ +#endif + case ARPHRD_IEEE802_TR: + case ARPHRD_IEEE802: + handle->linktype = DLT_IEEE802; + handle->offset = 2; + break; + + case ARPHRD_ARCNET: + handle->linktype = DLT_ARCNET_LINUX; + break; + +#ifndef ARPHRD_FDDI /* From Linux 2.2.13 */ +#define ARPHRD_FDDI 774 +#endif + case ARPHRD_FDDI: + handle->linktype = DLT_FDDI; + handle->offset = 3; + break; #ifndef ARPHRD_ATM /* FIXME: How to #include this? */ #define ARPHRD_ATM 19 #endif - case ARPHRD_ATM: return DLT_ATM_CLIP; + case ARPHRD_ATM: + /* + * The Classical IP implementation in ATM for Linux + * supports both what RFC 1483 calls "LLC Encapsulation", + * in which each packet has an LLC header, possibly + * with a SNAP header as well, prepended to it, and + * what RFC 1483 calls "VC Based Multiplexing", in which + * different virtual circuits carry different network + * layer protocols, and no header is prepended to packets. + * + * They both have an ARPHRD_ type of ARPHRD_ATM, so + * you can't use the ARPHRD_ type to find out whether + * captured packets will have an LLC header, and, + * while there's a socket ioctl to *set* the encapsulation + * type, there's no ioctl to *get* the encapsulation type. + * + * This means that + * + * programs that dissect Linux Classical IP frames + * would have to check for an LLC header and, + * depending on whether they see one or not, dissect + * the frame as LLC-encapsulated or as raw IP (I + * don't know whether there's any traffic other than + * IP that would show up on the socket, or whether + * there's any support for IPv6 in the Linux + * Classical IP code); + * + * filter expressions would have to compile into + * code that checks for an LLC header and does + * the right thing. + * + * Both of those are a nuisance - and, at least on systems + * that support PF_PACKET sockets, we don't have to put + * up with those nuisances; instead, we can just capture + * in cooked mode. That's what we'll do, if we can. + * Otherwise, we'll just fail. + */ + if (cooked_ok) + handle->linktype = DLT_LINUX_SLL; + else + handle->linktype = -1; + break; + +#ifndef ARPHRD_IEEE80211 /* From Linux 2.4.6 */ +#define ARPHRD_IEEE80211 801 +#endif + case ARPHRD_IEEE80211: + handle->linktype = DLT_IEEE802_11; + break; + +#ifndef ARPHRD_IEEE80211_PRISM /* From Linux 2.4.18 */ +#define ARPHRD_IEEE80211_PRISM 802 +#endif + case ARPHRD_IEEE80211_PRISM: + handle->linktype = DLT_PRISM_HEADER; + break; case ARPHRD_PPP: + /* + * Some PPP code in the kernel supplies no link-layer + * header whatsoever to PF_PACKET sockets; other PPP + * code supplies PPP link-layer headers ("syncppp.c"); + * some PPP code might supply random link-layer + * headers (PPP over ISDN - there's code in Ethereal, + * for example, to cope with PPP-over-ISDN captures + * with which the Ethereal developers have had to cope, + * heuristically trying to determine which of the + * oddball link-layer headers particular packets have). + * + * As such, we just punt, and run all PPP interfaces + * in cooked mode, if we can; otherwise, we just treat + * it as DLT_RAW, for now - if somebody needs to capture, + * on a 2.0[.x] kernel, on PPP devices that supply a + * link-layer header, they'll have to add code here to + * map to the appropriate DLT_ type (possibly adding a + * new DLT_ type, if necessary). + */ + if (cooked_ok) + handle->linktype = DLT_LINUX_SLL; + else { + /* + * XXX - handle ISDN types here? We can't fall + * back on cooked sockets, so we'd have to + * figure out from the device name what type of + * link-layer encapsulation it's using, and map + * that to an appropriate DLT_ value, meaning + * we'd map "isdnN" devices to DLT_RAW (they + * supply raw IP packets with no link-layer + * header) and "isdY" devices to a new DLT_I4L_IP + * type that has only an Ethernet packet type as + * a link-layer header. + * + * But sometimes we seem to get random crap + * in the link-layer header when capturing on + * ISDN devices.... + */ + handle->linktype = DLT_RAW; + } + break; + +#ifndef ARPHRD_CISCO +#define ARPHRD_CISCO 513 /* previously ARPHRD_HDLC */ +#endif + case ARPHRD_CISCO: + handle->linktype = DLT_C_HDLC; + break; + + /* Not sure if this is correct for all tunnels, but it + * works for CIPE */ + case ARPHRD_TUNNEL: +#ifndef ARPHRD_SIT +#define ARPHRD_SIT 776 /* From Linux 2.2.13 */ +#endif + case ARPHRD_SIT: case ARPHRD_CSLIP: case ARPHRD_SLIP6: case ARPHRD_CSLIP6: - case ARPHRD_SLIP: return DLT_RAW; - } + case ARPHRD_ADAPT: + case ARPHRD_SLIP: +#ifndef ARPHRD_RAWHDLC +#define ARPHRD_RAWHDLC 518 +#endif + case ARPHRD_RAWHDLC: +#ifndef ARPHRD_DLCI +#define ARPHRD_DLCI 15 +#endif + case ARPHRD_DLCI: + /* + * XXX - should some of those be mapped to DLT_LINUX_SLL + * instead? Should we just map all of them to DLT_LINUX_SLL? + */ + handle->linktype = DLT_RAW; + break; + +#ifndef ARPHRD_FRAD +#define ARPHRD_FRAD 770 +#endif + case ARPHRD_FRAD: + handle->linktype = DLT_FRELAY; + break; + + case ARPHRD_LOCALTLK: + handle->linktype = DLT_LTALK; + break; + +#ifndef ARPHRD_FCPP +#define ARPHRD_FCPP 784 +#endif + case ARPHRD_FCPP: +#ifndef ARPHRD_FCAL +#define ARPHRD_FCAL 785 +#endif + case ARPHRD_FCAL: +#ifndef ARPHRD_FCPL +#define ARPHRD_FCPL 786 +#endif + case ARPHRD_FCPL: +#ifndef ARPHRD_FCFABRIC +#define ARPHRD_FCFABRIC 787 +#endif + case ARPHRD_FCFABRIC: + /* + * We assume that those all mean RFC 2625 IP-over- + * Fibre Channel, with the RFC 2625 header at + * the beginning of the packet. + */ + handle->linktype = DLT_IP_OVER_FC; + break; - return -1; +#ifndef ARPHRD_IRDA +#define ARPHRD_IRDA 783 +#endif + case ARPHRD_IRDA: + /* Don't expect IP packet out of this interfaces... */ + handle->linktype = DLT_LINUX_IRDA; + /* We need to save packet direction for IrDA decoding, + * so let's use "Linux-cooked" mode. Jean II */ + //handle->md.cooked = 1; + break; + + default: + handle->linktype = -1; + break; + } } /* ===== Functions to interface to the newer kernels ================== */ @@ -502,11 +1265,13 @@ static int map_arphrd_to_dlt(int arptype) * FIXME: 0 uses to mean success (Sebastian) */ static int -live_open_new(pcap_t *handle, char *device, int promisc, +live_open_new(pcap_t *handle, const char *device, int promisc, int to_ms, char *ebuf) { -#ifdef HAVE_NETPACKET_PACKET_H - int sock_fd = -1, device_id, mtu, arptype; +#ifdef HAVE_PF_PACKET_SOCKETS + int sock_fd = -1, arptype; + int err; + int fatal_err = 0; struct packet_mreq mr; /* One shot loop used for error handling - bail out with break */ @@ -514,10 +1279,10 @@ live_open_new(pcap_t *handle, char *device, int promisc, do { /* * Open a socket with protocol family packet. If a device is - * given we try to open it in raw mode otherwise we use - * the cooked interface. + * given we try to open it in raw mode otherwise we use + * the cooked interface. */ - sock_fd = device ? + sock_fd = device ? socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)) : socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL)); @@ -531,90 +1296,163 @@ live_open_new(pcap_t *handle, char *device, int promisc, handle->md.sock_packet = 0; /* - * What kind of frames do we have to deal with? Fall back - * to cooked mode if we have an unknown interface type. + * Get the interface index of the loopback device. + * If the attempt fails, don't fail, just set the + * "md.lo_ifindex" to -1. + * + * XXX - can there be more than one device that loops + * packets back, i.e. devices other than "lo"? If so, + * we'd need to find them all, and have an array of + * indices for them, and check all of them in + * "pcap_read_packet()". + */ + handle->md.lo_ifindex = iface_get_id(sock_fd, "lo", ebuf); + + /* + * Default value for offset to align link-layer payload + * on a 4-byte boundary. + */ + handle->offset = 0; + + /* + * What kind of frames do we have to deal with? Fall back + * to cooked mode if we have an unknown interface type. */ if (device) { + /* Assume for now we don't need cooked mode. */ + handle->md.cooked = 0; + arptype = iface_get_arptype(sock_fd, device, ebuf); - if (arptype == -1) - break; - handle->linktype = map_arphrd_to_dlt(arptype); - } else - handle->linktype = PCAP_ENCAP_RAW; - - if (handle->linktype == -1) { - /* Unknown interface type - reopen in cooked mode */ - - if (close(sock_fd) == -1) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, - "close: %s", pcap_strerror(errno)); + if (arptype == -1) { + fatal_err = 1; break; } - sock_fd = socket(PF_PACKET, SOCK_DGRAM, - htons(ETH_P_ALL)); - if (sock_fd == -1) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, - "socket: %s", pcap_strerror(errno)); - break; - } - - fprintf(stderr, - "Warning: Falling back to cooked socket\n"); - handle->linktype = DLT_RAW; - } + map_arphrd_to_dlt(handle, arptype, 1); + if (handle->linktype == -1 || + handle->linktype == DLT_LINUX_SLL || + handle->linktype == DLT_LINUX_IRDA || + (handle->linktype == DLT_EN10MB && + (strncmp("isdn", device, 4) == 0 || + strncmp("isdY", device, 4) == 0))) { + /* + * Unknown interface type (-1), or a + * device we explicitly chose to run + * in cooked mode (e.g., PPP devices), + * or an ISDN device (whose link-layer + * type we can only determine by using + * APIs that may be different on different + * kernels) - reopen in cooked mode. + */ + if (close(sock_fd) == -1) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "close: %s", pcap_strerror(errno)); + break; + } + sock_fd = socket(PF_PACKET, SOCK_DGRAM, + htons(ETH_P_ALL)); + if (sock_fd == -1) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "socket: %s", pcap_strerror(errno)); + break; + } + handle->md.cooked = 1; + + /* + * Get rid of any link-layer type list + * we allocated - this only supports cooked + * capture. + */ + if (handle->dlt_list != NULL) { + free(handle->dlt_list); + handle->dlt_list = NULL; + handle->dlt_count = 0; + } + if (handle->linktype == -1) { + /* + * Warn that we're falling back on + * cooked mode; we may want to + * update "map_arphrd_to_dlt()" + * to handle the new type. + */ + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "arptype %d not " + "supported by libpcap - " + "falling back to cooked " + "socket", + arptype); + } + /* IrDA capture is not a real "cooked" capture, + * it's IrLAP frames, not IP packets. */ + if (handle->linktype != DLT_LINUX_IRDA) + handle->linktype = DLT_LINUX_SLL; + } - if (device) { - device_id = iface_get_id(sock_fd, device, ebuf); - if (device_id == -1) + handle->md.ifindex = iface_get_id(sock_fd, device, ebuf); + if (handle->md.ifindex == -1) break; - if (iface_bind(sock_fd, device_id, ebuf) == -1) + if ((err = iface_bind(sock_fd, handle->md.ifindex, + ebuf)) < 0) { + if (err == -2) + fatal_err = 1; break; + } + } else { + /* + * This is cooked mode. + */ + handle->md.cooked = 1; + handle->linktype = DLT_LINUX_SLL; + + /* + * We're not bound to a device. + * XXX - true? Or true only if we're using + * the "any" device? + * For now, we're using this as an indication + * that we can't transmit; stop doing that only + * if we figure out how to transmit in cooked + * mode. + */ + handle->md.ifindex = -1; } - /* Select promiscous mode on/off */ + /* + * Select promiscuous mode on if "promisc" is set. + * + * Do not turn allmulti mode on if we don't select + * promiscuous mode - on some devices (e.g., Orinoco + * wireless interfaces), allmulti mode isn't supported + * and the driver implements it by turning promiscuous + * mode on, and that screws up the operation of the + * card as a normal networking interface, and on no + * other platform I know of does starting a non- + * promiscuous capture affect which multicast packets + * are received by the interface. + */ -#ifdef SOL_PACKET - /* + /* * Hmm, how can we set promiscuous mode on all interfaces? * I am not sure if that is possible at all. */ - if (device) { + if (device && promisc) { memset(&mr, 0, sizeof(mr)); - mr.mr_ifindex = device_id; - mr.mr_type = promisc ? - PACKET_MR_PROMISC : PACKET_MR_ALLMULTI; - if (setsockopt(sock_fd, SOL_PACKET, + mr.mr_ifindex = handle->md.ifindex; + mr.mr_type = PACKET_MR_PROMISC; + if (setsockopt(sock_fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mr, sizeof(mr)) == -1) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, + snprintf(ebuf, PCAP_ERRBUF_SIZE, "setsockopt: %s", pcap_strerror(errno)); break; } } -#endif - - /* Compute the buffersize */ - mtu = iface_get_mtu(sock_fd, device, ebuf); - if (mtu == -1) - break; - handle->bufsize = MAX_LINKHEADER_SIZE + mtu; - - /* Fill in the pcap structure */ + /* Save the socket FD in the pcap structure */ handle->fd = sock_fd; - handle->offset = 0; - - handle->buffer = malloc(handle->bufsize); - if (!handle->buffer) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, - "malloc: %s", pcap_strerror(errno)); - break; - } return 1; @@ -622,18 +1460,27 @@ live_open_new(pcap_t *handle, char *device, int promisc, if (sock_fd != -1) close(sock_fd); - return 0; + + if (fatal_err) { + /* + * Get rid of any link-layer type list we allocated. + */ + if (handle->dlt_list != NULL) + free(handle->dlt_list); + return -2; + } else + return 0; #else - strncpy(ebuf, - "New packet capturing interface not supported by build " + strncpy(ebuf, + "New packet capturing interface not supported by build " "environment", PCAP_ERRBUF_SIZE); return 0; #endif } -#ifdef HAVE_NETPACKET_PACKET_H +#ifdef HAVE_PF_PACKET_SOCKETS /* - * Return the index of the given device name. Fill ebuf and return + * Return the index of the given device name. Fill ebuf and return * -1 on failure. */ static int @@ -654,12 +1501,14 @@ iface_get_id(int fd, const char *device, char *ebuf) } /* - * Bind the socket associated with FD to the given device. + * Bind the socket associated with FD to the given device. */ static int iface_bind(int fd, int ifindex, char *ebuf) { struct sockaddr_ll sll; + int err; + socklen_t errlen = sizeof(err); memset(&sll, 0, sizeof(sll)); sll.sll_family = AF_PACKET; @@ -672,6 +1521,20 @@ iface_bind(int fd, int ifindex, char *ebuf) return -1; } + /* Any pending errors, e.g., network is down? */ + + if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "getsockopt: %s", pcap_strerror(errno)); + return -2; + } + + if (err > 0) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "bind: %s", pcap_strerror(err)); + return -2; + } + return 0; } @@ -683,32 +1546,105 @@ iface_bind(int fd, int ifindex, char *ebuf) /* * With older kernels promiscuous mode is kind of interesting because we * have to reset the interface before exiting. The problem can't really - * be solved without some daemon taking care of managing usage counts. - * We save the promiscuous state of the device when opening the capture - * stream and arrange for it to be reset on process exit. - * - * XXX: This solution is still not correct even for this case. The - * devices stay in promiscuous mode until the process exits. I need to - * modify pcap_close to solve this. + * be solved without some daemon taking care of managing usage counts. + * If we put the interface into promiscuous mode, we set a flag indicating + * that we must take it out of that mode when the interface is closed, + * and, when closing the interface, if that flag is set we take it out + * of promiscuous mode. */ -/* - * The device name and the interface flags to be restored at exit +/* + * List of pcaps for which we turned promiscuous mode on by hand. + * If there are any such pcaps, we arrange to call "pcap_close_all()" + * when we exit, and have it close all of them to turn promiscuous mode + * off. + */ +static struct pcap *pcaps_to_close; + +/* + * TRUE if we've already called "atexit()" to cause "pcap_close_all()" to + * be called on exit. */ -struct ifreq restore_ifr; +static int did_atexit; -static void restore_interface( void ) +static void pcap_close_all(void) { - int status = socket(PF_INET, SOCK_PACKET, 0); + struct pcap *handle; - if (status != -1) - status = ioctl(status, SIOCSIFFLAGS, &restore_ifr); + while ((handle = pcaps_to_close) != NULL) + pcap_close(handle); +} + +static void pcap_close_linux( pcap_t *handle ) +{ + struct pcap *p, *prevp; + struct ifreq ifr; + + if (handle->md.clear_promisc) { + /* + * We put the interface into promiscuous mode; take + * it out of promiscuous mode. + * + * XXX - if somebody else wants it in promiscuous mode, + * this code cannot know that, so it'll take it out + * of promiscuous mode. That's not fixable in 2.0[.x] + * kernels. + */ + memset(&ifr, 0, sizeof(ifr)); + strncpy(ifr.ifr_name, handle->md.device, sizeof(ifr.ifr_name)); + if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) { + fprintf(stderr, + "Can't restore interface flags (SIOCGIFFLAGS failed: %s).\n" + "Please adjust manually.\n" + "Hint: This can't happen with Linux >= 2.2.0.\n", + strerror(errno)); + } else { + if (ifr.ifr_flags & IFF_PROMISC) { + /* + * Promiscuous mode is currently on; turn it + * off. + */ + ifr.ifr_flags &= ~IFF_PROMISC; + if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) { + fprintf(stderr, + "Can't restore interface flags (SIOCSIFFLAGS failed: %s).\n" + "Please adjust manually.\n" + "Hint: This can't happen with Linux >= 2.2.0.\n", + strerror(errno)); + } + } + } - if (status == -1) { - fprintf(stderr, - "Can't restore interface flags. Please adjust manually. \n" - "Hint: This can't happen with Linux >= 2.2.0.\n"); + /* + * Take this pcap out of the list of pcaps for which we + * have to take the interface out of promiscuous mode. + */ + for (p = pcaps_to_close, prevp = NULL; p != NULL; + prevp = p, p = p->md.next) { + if (p == handle) { + /* + * Found it. Remove it from the list. + */ + if (prevp == NULL) { + /* + * It was at the head of the list. + */ + pcaps_to_close = p->md.next; + } else { + /* + * It was in the middle of the list. + */ + prevp->md.next = p->md.next; + } + break; + } + } } + + if (handle->md.device != NULL) + free(handle->md.device); + handle->md.device = NULL; + pcap_close_common(handle); } /* @@ -717,17 +1653,17 @@ static void restore_interface( void ) * FIXME: 0 uses to mean success (Sebastian) */ static int -live_open_old(pcap_t *handle, char *device, int promisc, +live_open_old(pcap_t *handle, const char *device, int promisc, int to_ms, char *ebuf) { - int sock_fd = -1, mtu, arptype; + int arptype; struct ifreq ifr; do { /* Open the socket */ - - sock_fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL)); - if (sock_fd == -1) { + + handle->fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL)); + if (handle->fd == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "socket: %s", pcap_strerror(errno)); break; @@ -736,89 +1672,117 @@ live_open_old(pcap_t *handle, char *device, int promisc, /* It worked - we are using the old interface */ handle->md.sock_packet = 1; + /* ...which means we get the link-layer header. */ + handle->md.cooked = 0; + /* Bind to the given device */ if (!device) { - strncpy(ebuf, "pcap_open_live: No interface given", + strncpy(ebuf, "pcap_open_live: The \"any\" device isn't supported on 2.0[.x]-kernel systems", PCAP_ERRBUF_SIZE); break; } - if (iface_bind_old(sock_fd, device, ebuf) == -1) + if (iface_bind_old(handle->fd, device, ebuf) == -1) break; - /* Go to promisc mode */ + /* + * Try to get the link-layer type. + */ + arptype = iface_get_arptype(handle->fd, device, ebuf); + if (arptype == -1) + break; + + /* + * Try to find the DLT_ type corresponding to that + * link-layer type. + */ + map_arphrd_to_dlt(handle, arptype, 0); + if (handle->linktype == -1) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "unknown arptype %d", arptype); + break; + } + + /* Go to promisc mode if requested */ + if (promisc) { memset(&ifr, 0, sizeof(ifr)); strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); - if (ioctl(sock_fd, SIOCGIFFLAGS, &ifr) == -1) { + if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "ioctl: %s", pcap_strerror(errno)); break; } if ((ifr.ifr_flags & IFF_PROMISC) == 0) { - restore_ifr = ifr; + /* + * Promiscuous mode isn't currently on, + * so turn it on, and remember that + * we should turn it off when the + * pcap_t is closed. + */ + + /* + * If we haven't already done so, arrange + * to have "pcap_close_all()" called when + * we exit. + */ + if (!did_atexit) { + if (atexit(pcap_close_all) == -1) { + /* + * "atexit()" failed; don't + * put the interface in + * promiscuous mode, just + * give up. + */ + strncpy(ebuf, "atexit failed", + PCAP_ERRBUF_SIZE); + break; + } + did_atexit = 1; + } + ifr.ifr_flags |= IFF_PROMISC; - if (ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1) { + if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "ioctl: %s", pcap_strerror(errno)); break; } - if (atexit(restore_interface) == -1) { - restore_interface(); - strncpy(ebuf, "atexit failed", - PCAP_ERRBUF_SIZE); - break; - } + handle->md.clear_promisc = 1; + + /* + * Add this to the list of pcaps + * to close when we exit. + */ + handle->md.next = pcaps_to_close; + pcaps_to_close = handle; } } - - /* Compute the buffersize */ - - mtu = iface_get_mtu(sock_fd, device, ebuf); - if (mtu == -1) - break; - handle->bufsize = MAX_LINKHEADER_SIZE + mtu; - - /* All done - fill in the pcap handle */ - - arptype = iface_get_arptype(sock_fd, device, ebuf); - if (arptype == -1) - break; - - handle->fd = sock_fd; + /* + * Default value for offset to align link-layer payload + * on a 4-byte boundary. + */ handle->offset = 0; - handle->linktype = map_arphrd_to_dlt(arptype); - if (handle->linktype == -1) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, - "interface type of %s not supported", device); - break; - } - handle->buffer = malloc(handle->bufsize); - if (!handle->buffer) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, - "malloc: %s", pcap_strerror(errno)); - break; - } return 1; - + } while (0); - - if (sock_fd != -1) - close(sock_fd); + + pcap_close_linux(handle); return 0; } /* - * Bind the socket associated with FD to the given device using the + * Bind the socket associated with FD to the given device using the * interface of the old kernels. */ static int iface_bind_old(int fd, const char *device, char *ebuf) { struct sockaddr saddr; + int err; + socklen_t errlen = sizeof(err); memset(&saddr, 0, sizeof(saddr)); strncpy(saddr.sa_data, device, sizeof(saddr.sa_data)); @@ -828,6 +1792,20 @@ iface_bind_old(int fd, const char *device, char *ebuf) return -1; } + /* Any pending errors, e.g., network is down? */ + + if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "getsockopt: %s", pcap_strerror(errno)); + return -1; + } + + if (err > 0) { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "bind: %s", pcap_strerror(err)); + return -1; + } + return 0; } @@ -835,7 +1813,7 @@ iface_bind_old(int fd, const char *device, char *ebuf) /* ===== System calls available on all supported kernels ============== */ /* - * Query the kernel for the MTU of the given interface. + * Query the kernel for the MTU of the given interface. */ static int iface_get_mtu(int fd, const char *device, char *ebuf) @@ -876,3 +1854,241 @@ iface_get_arptype(int fd, const char *device, char *ebuf) return ifr.ifr_hwaddr.sa_family; } + +#ifdef SO_ATTACH_FILTER +static int +fix_program(pcap_t *handle, struct sock_fprog *fcode) +{ + size_t prog_size; + register int i; + register struct bpf_insn *p; + struct bpf_insn *f; + int len; + + /* + * Make a copy of the filter, and modify that copy if + * necessary. + */ + prog_size = sizeof(*handle->fcode.bf_insns) * handle->fcode.bf_len; + len = handle->fcode.bf_len; + f = (struct bpf_insn *)malloc(prog_size); + if (f == NULL) { + snprintf(handle->errbuf, sizeof(handle->errbuf), + "malloc: %s", pcap_strerror(errno)); + return -1; + } + memcpy(f, handle->fcode.bf_insns, prog_size); + fcode->len = len; + fcode->filter = (struct sock_filter *) f; + + for (i = 0; i < len; ++i) { + p = &f[i]; + /* + * What type of instruction is this? + */ + switch (BPF_CLASS(p->code)) { + + case BPF_RET: + /* + * It's a return instruction; is the snapshot + * length a constant, rather than the contents + * of the accumulator? + */ + if (BPF_MODE(p->code) == BPF_K) { + /* + * Yes - if the value to be returned, + * i.e. the snapshot length, is anything + * other than 0, make it 65535, so that + * the packet is truncated by "recvfrom()", + * not by the filter. + * + * XXX - there's nothing we can easily do + * if it's getting the value from the + * accumulator; we'd have to insert + * code to force non-zero values to be + * 65535. + */ + if (p->k != 0) + p->k = 65535; + } + break; + + case BPF_LD: + case BPF_LDX: + /* + * It's a load instruction; is it loading + * from the packet? + */ + switch (BPF_MODE(p->code)) { + + case BPF_ABS: + case BPF_IND: + case BPF_MSH: + /* + * Yes; are we in cooked mode? + */ + if (handle->md.cooked) { + /* + * Yes, so we need to fix this + * instruction. + */ + if (fix_offset(p) < 0) { + /* + * We failed to do so. + * Return 0, so our caller + * knows to punt to userland. + */ + return 0; + } + } + break; + } + break; + } + } + return 1; /* we succeeded */ +} + +static int +fix_offset(struct bpf_insn *p) +{ + /* + * What's the offset? + */ + if (p->k >= SLL_HDR_LEN) { + /* + * It's within the link-layer payload; that starts at an + * offset of 0, as far as the kernel packet filter is + * concerned, so subtract the length of the link-layer + * header. + */ + p->k -= SLL_HDR_LEN; + } else if (p->k == 14) { + /* + * It's the protocol field; map it to the special magic + * kernel offset for that field. + */ + p->k = SKF_AD_OFF + SKF_AD_PROTOCOL; + } else { + /* + * It's within the header, but it's not one of those + * fields; we can't do that in the kernel, so punt + * to userland. + */ + return -1; + } + return 0; +} + +static int +set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode) +{ + int total_filter_on = 0; + int save_mode; + int ret; + int save_errno; + + /* + * The socket filter code doesn't discard all packets queued + * up on the socket when the filter is changed; this means + * that packets that don't match the new filter may show up + * after the new filter is put onto the socket, if those + * packets haven't yet been read. + * + * This means, for example, that if you do a tcpdump capture + * with a filter, the first few packets in the capture might + * be packets that wouldn't have passed the filter. + * + * We therefore discard all packets queued up on the socket + * when setting a kernel filter. (This isn't an issue for + * userland filters, as the userland filtering is done after + * packets are queued up.) + * + * To flush those packets, we put the socket in read-only mode, + * and read packets from the socket until there are no more to + * read. + * + * In order to keep that from being an infinite loop - i.e., + * to keep more packets from arriving while we're draining + * the queue - we put the "total filter", which is a filter + * that rejects all packets, onto the socket before draining + * the queue. + * + * This code deliberately ignores any errors, so that you may + * get bogus packets if an error occurs, rather than having + * the filtering done in userland even if it could have been + * done in the kernel. + */ + if (setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER, + &total_fcode, sizeof(total_fcode)) == 0) { + char drain[1]; + + /* + * Note that we've put the total filter onto the socket. + */ + total_filter_on = 1; + + /* + * Save the socket's current mode, and put it in + * non-blocking mode; we drain it by reading packets + * until we get an error (which is normally a + * "nothing more to be read" error). + */ + save_mode = fcntl(handle->fd, F_GETFL, 0); + if (save_mode != -1 && + fcntl(handle->fd, F_SETFL, save_mode | O_NONBLOCK) >= 0) { + while (recv(handle->fd, &drain, sizeof drain, + MSG_TRUNC) >= 0) + ; + save_errno = errno; + fcntl(handle->fd, F_SETFL, save_mode); + if (save_errno != EAGAIN) { + /* Fatal error */ + reset_kernel_filter(handle); + snprintf(handle->errbuf, sizeof(handle->errbuf), + "recv: %s", pcap_strerror(save_errno)); + return -2; + } + } + } + + /* + * Now attach the new filter. + */ + ret = setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER, + fcode, sizeof(*fcode)); + if (ret == -1 && total_filter_on) { + /* + * Well, we couldn't set that filter on the socket, + * but we could set the total filter on the socket. + * + * This could, for example, mean that the filter was + * too big to put into the kernel, so we'll have to + * filter in userland; in any case, we'll be doing + * filtering in userland, so we need to remove the + * total filter so we see packets. + */ + save_errno = errno; + + /* + * XXX - if this fails, we're really screwed; + * we have the total filter on the socket, + * and it won't come off. What do we do then? + */ + reset_kernel_filter(handle); + + errno = save_errno; + } + return ret; +} + +static int +reset_kernel_filter(pcap_t *handle) +{ + /* setsockopt() barfs unless it get a dummy parameter */ + int dummy; + + return setsockopt(handle->fd, SOL_SOCKET, SO_DETACH_FILTER, + &dummy, sizeof(dummy)); +} +#endif