X-Git-Url: https://git.tcpdump.org/libpcap/blobdiff_plain/b59cd6dc3cb8d2bf6e98c664dbf19f73dbc3b275..bc61a9fd3752e56c5b7dd9ef27ae53fcb51f9bf4:/pcap-linux.c diff --git a/pcap-linux.c b/pcap-linux.c index c5f1d792..89446291 100644 --- a/pcap-linux.c +++ b/pcap-linux.c @@ -1,50 +1,75 @@ /* - pcap-linux.c: Packet capture interface to the Linux kernel - 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 - notice, this list of conditions and the following disclaimer in - the documentation and/or other materials provided with the - distribution. - 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. -*/ - -/* - TODO: - - - Make it compatible with older Linux installations (at compilation time) - - BUGS: - - - setting promiscuous on loopback for example gives every packet - twice -*/ - + * pcap-linux.c: Packet capture interface to the Linux kernel + * + * 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 + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 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 1.70 2001-10-25 08:27:18 guy Exp $ (LBL)"; +#endif /* - FYI: - - pcap_read currently reads 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. -*/ + * 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. + */ #ifdef HAVE_CONFIG_H @@ -52,6 +77,7 @@ #endif #include "pcap-int.h" +#include "sll.h" #include #include @@ -60,14 +86,55 @@ #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 @@ -78,43 +145,80 @@ 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 #define MAX_LINKHEADER_SIZE 256 -/* 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 int pcap_read_packet( pcap_t *, pcap_handler, u_char * ); +/* + * 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. + */ +#define BIGGER_THAN_ALL_MTUS (64*1024) -/* Wrap some ioctl calls */ -static int iface_get_id( int fd, const char *device, char *ebuf ); -static int iface_get_mtu( int fd, const char *device, char *ebuf ); -static int iface_get_arptype( int fd, const char *device, char *ebuf ); -static int iface_bind( int fd, int ifindex, char *ebuf ); -static int iface_bind_old( int fd, const char *device, char *ebuf ); +/* + * Prototypes for internal functions + */ +static void map_arphrd_to_dlt(pcap_t *, int); +static int live_open_old(pcap_t *, char *, int, int, char *); +static int live_open_new(pcap_t *, char *, int, int, char *); +static int pcap_read_packet(pcap_t *, pcap_handler, u_char *); /* - pcap_open_live: + * 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); - 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 - be deprecated and functions be added to select that later allow - modification of that values -- Torsten). +#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 - See also pcap(3). -*/ +/* + * 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 + * 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(char *device, int snaplen, int promisc, int to_ms, char *ebuf) { + pcap_t *handle; + int mtu; + struct utsname utsname; + /* Allocate a handle for this session. */ - - pcap_t *handle = malloc(sizeof(*handle)); - if( handle == NULL ) { + + handle = malloc(sizeof(*handle)); + if (handle == NULL) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s", pcap_strerror(errno)); return NULL; @@ -122,145 +226,215 @@ pcap_open_live( char *device, int snaplen, int promisc, int to_ms, char *ebuf ) /* Initialize some components of the pcap structure. */ - memset( handle, 0, sizeof(*handle) ); + memset(handle, 0, sizeof(*handle)); handle->snapshot = snaplen; handle->md.timeout = to_ms; - handle->md.promisc = promisc; - handle->md.device = strdup( device ); - if( handle->md.device == NULL ) { + + /* + * 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); + + if (handle->md.device == NULL) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "strdup: %s", pcap_strerror(errno) ); - free( handle ); + free(handle); return NULL; } - /* Current Linux kernels use the protocol family PF_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 - * trying both methods with the newer method preferred. */ - - if( ! (live_open_new(handle, device, promisc, to_ms, ebuf) || + * 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)) ) { - /* Both methods to open the packet socket failed. Tidy + /* + * 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); - free( handle ); + 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 once. */ - - 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) { + close(handle->fd); + free(handle->md.device); + 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)); + close(handle->fd); + free(handle->md.device); + free(handle); + return NULL; } return handle; } /* - pcap_read: - - 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... -*/ + * 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. + */ int pcap_read(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user) { - int status, packets; - fd_set read_fds; - struct timeval tv; - - if( handle->md.timeout > 0 ) { - tv.tv_usec = (handle->md.timeout % 1000) * 1000; - tv.tv_sec = (handle->md.timeout / 1000); - } - - for( packets = 0; max_packets == -1 || packets < max_packets; ) - { - status = pcap_read_packet( handle, callback, user ); - - if( status > 0 ) { - packets++; - continue; - } else if( status == -1 ) - return -1; - - /* paranoia - the recvmsg call should block if we don't use - * a timeout */ - if( handle->md.timeout <= 0 ) - continue; - - /* No packet available - go to sleep */ - 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; + /* + * Currently, on Linux only one packet is delivered per read, + * so we don't loop. + */ + return pcap_read_packet(handle, callback, user); } - -/* - pcap_read_packet: - Read a packet from the socket calling the handler provided by - the user. Returns 0 if no packet was there, 1 if a packet was - handled and -1 if an error occured. -*/ +/* + * 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 ) +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; - /* We don't currently use the from return value of recvfrom but - * this will probably implemented in the future. */ - +#ifdef HAVE_PF_PACKET_SOCKETS + /* + * 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 { fromlen = sizeof(from); packet_len = recvfrom( - handle->fd, handle->buffer + handle->offset, - handle->snapshot, MSG_TRUNC, - (struct sockaddr *) &from, &fromlen ); - } while( packet_len == -1 && errno == EINTR ); - - /* Check if some error occured */ - if( packet_len == -1 ) { - if( errno == EAGAIN ) + handle->fd, bp + offset, + handle->bufsize - offset, MSG_TRUNC, + (struct sockaddr *) &from, &fromlen); + } while (packet_len == -1 && errno == EINTR); + + /* Check if an error occured */ + + if (packet_len == -1) { + if (errno == EAGAIN) return 0; /* no packet there */ else { snprintf(handle->errbuf, sizeof(handle->errbuf), @@ -269,188 +443,538 @@ pcap_read_packet( pcap_t *handle, pcap_handler callback, u_char *userdata ) } } - /* XXX: According to the kernel source we should get the real +#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 + /* + * 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: + * + * 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 + * first - and there lies the problem. The default filter always + * cuts the packet at the snaplen: + * + * # tcpdump -d + * (000) ret #68 + * + * 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. + * + * 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 ) + 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, - packet_len, caplen) == 0 ) + if (!handle->md.use_bpf && handle->fcode.bf_insns) { + 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 ) { + + if (ioctl(handle->fd, SIOCGSTAMP, &pcap_header.ts) == -1) { snprintf(handle->errbuf, sizeof(handle->errbuf), "ioctl: %s", pcap_strerror(errno)); return -1; } 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; } /* - pcap_stats: - - Get the statistics for the given packet capture handle. -*/ + * Get the statistics for the given packet capture handle. + * 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 ) +pcap_stats(pcap_t *handle, struct pcap_stat *stats) { +#ifdef HAVE_TPACKET_STATS + struct tpacket_stats kstats; + socklen_t len; + + /* + * Try to get the packet counts from the kernel. + */ + if (getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS, + &kstats, &len) > -1) { + handle->md.stat.ps_recv = (kstats.tp_packets - kstats.tp_drops); + handle->md.stat.ps_drop = kstats.tp_drops; + } +#endif + /* + * "ps_recv" counts only packets that passed the filter. + * + * "ps_drop" is maintained only on systems that support + * the PACKET_STATISTICS "getsockopt()" argument. + */ *stats = handle->md.stat; return 0; } /* - pcap_setfilter: - - Attach the given BPF code to the packet capture device. -*/ + * Attach the given BPF code to the packet capture device. + */ int -pcap_setfilter( pcap_t *handle, struct bpf_program *filter ) +pcap_setfilter(pcap_t *handle, struct bpf_program *filter) { #ifdef SO_ATTACH_FILTER struct sock_fprog fcode; + int can_filter_in_kernel; #endif - if( !handle ) + if (!handle) return -1; - if( !filter ) { + if (!filter) { strncpy(handle->errbuf, "setfilter: No filter specified", sizeof(handle->errbuf)); 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 ) { + + if (install_bpf_program(handle, filter) < 0) { snprintf(handle->errbuf, sizeof(handle->errbuf), "malloc: %s", pcap_strerror(errno)); 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; + /* + * If we're reading from a savefile, don't try to install + * a kernel filter. + */ + if (handle->sf.rfile != NULL) + return 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; - if( filter->bf_len > USHRT_MAX ) { - fprintf( stderr, "Warning: Filter to complex for kernel\n" ); - /* paranoid - should never happen */ - } - else if( setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER, - &fcode, sizeof(fcode)) == 0 ) - { - handle->md.use_bpf = 1; +#ifdef 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. + */ + 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. */ - if( errno != ENOPROTOOPT && errno != EOPNOTSUPP ) { - fprintf( stderr, "Warning: Kernel filter failed: %s\n", - pcap_strerror(errno) ); + /* + * 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. + */ + 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; + } + } + + if (can_filter_in_kernel) { + if (set_kernel_filter(handle, &fcode) == 0) + { + /* Installation succeded - using kernel filter. */ + handle->md.use_bpf = 1; + } + else + { + /* + * 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)); + } } } -#endif + + /* + * 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); +#endif /* SO_ATTACH_FILTER */ return 0; } - /* - map_arphrd_to_dlt: - - 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. -*/ -static int map_arphrd_to_dlt( int arptype ) + * 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.) + * + * Sets the link type to -1 if unable to map the type. + */ +static void map_arphrd_to_dlt(pcap_t *handle, int arptype) { - switch( arptype ) { + switch (arptype) { + case ARPHRD_ETHER: 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; + break; + + 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: + /* + * 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. + */ + handle->linktype = DLT_LINUX_SLL; + break; + +#ifndef ARPHRD_IEEE80211 /* From Linux 2.4.6 */ +#define ARPHRD_IEEE80211 801 +#endif + case ARPHRD_IEEE80211: + handle->linktype = DLT_IEEE802_11; + 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. + */ + handle->linktype = DLT_LINUX_SLL; + break; + + case ARPHRD_HDLC: + 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 2.2.14 */ +#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: + /* + * 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; + + case ARPHRD_LOCALTLK: + handle->linktype = DLT_LTALK; + break; + + default: + handle->linktype = -1; + break; } - - return -1; } /* ===== Functions to interface to the newer kernels ================== */ /* - live_open_new: - - Try to open a packet socket using the new kernel interface. - Returns 0 on failure. - FIXME: 0 uses to mean success (Sebastian) -*/ + * Try to open a packet socket using the new kernel interface. + * Returns 0 on failure. + * FIXME: 0 uses to mean success (Sebastian) + */ static int -live_open_new( pcap_t *handle, char *device, int promisc, - int to_ms, char *ebuf ) +live_open_new(pcap_t *handle, 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, device_id, arptype; struct packet_mreq mr; /* One shot loop used for error handling - bail out with break */ do { - - /* Open a socket with protocol family packet. */ - sock_fd = socket( PF_PACKET, SOCK_RAW, htons(ETH_P_ALL) ); - if( sock_fd == -1 ) { + /* + * 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. + */ + sock_fd = device ? + socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)) + : socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL)); + + if (sock_fd == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "socket: %s", pcap_strerror(errno) ); break; @@ -459,101 +983,140 @@ live_open_new( pcap_t *handle, char *device, int promisc, /* It seems the kernel supports the new interface. */ handle->md.sock_packet = 0; - /* Currently we only support monitoring a single interface. - * While the kernel can do more I want to reimplement the - * old features first before adding more. */ + /* + * 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; - if( !device ) { - snprintf(ebuf, PCAP_ERRBUF_SIZE, - "pcap_open_live: No device given" ); - break; - } + /* + * What kind of frames do we have to deal with? Fall back + * to cooked mode if we have an unknown interface type. + */ - /* 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 ); - 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)); + arptype = iface_get_arptype(sock_fd, device, ebuf); + if (arptype == -1) break; + map_arphrd_to_dlt(handle, arptype); + if (handle->linktype == -1 || + handle->linktype == DLT_LINUX_SLL || + (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; + + 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); + } + handle->linktype = DLT_LINUX_SLL; } - 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)); + + device_id = iface_get_id(sock_fd, device, ebuf); + if (device_id == -1) break; - } - fprintf( stderr, - "Warning: Falling back to cooked socket\n" ); - handle->linktype = DLT_RAW; + if (iface_bind(sock_fd, device_id, ebuf) == -1) + break; + } else { + /* + * This is cooked mode. + */ + handle->md.cooked = 1; + handle->linktype = DLT_LINUX_SLL; + + /* + * XXX - squelch GCC complaints about + * uninitialized variables; if we can't + * select promiscuous mode on all interfaces, + * we should move the code below into the + * "if (device)" branch of the "if" and + * get rid of the next statement. + */ + device_id = -1; } - - device_id = iface_get_id( sock_fd, device, ebuf ); - if( device_id == -1 ) - break; - - if( iface_bind(sock_fd, device_id, ebuf) == -1 ) - break; - - /* Select promiscous mode on/off */ - - /* XXX: We got reports that this does not work in 2.3.99. - * Need to investigate. Using ioctl to switch the promisc - * mode at device level costs us most of the benefits of - * using the new kernel interface. - * UPDATE: I found the bug. The kernel checks mr_alen - * even if it is of zero interest for the request. A - * random value there made the kernel return EINVAL. - * Probably the right solution is to memset the whole - * struct at first. */ - - 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, PACKET_ADD_MEMBERSHIP, - &mr, sizeof(mr) ) == -1 ) - { - snprintf(ebuf, PCAP_ERRBUF_SIZE, - "setsockopt: %s", pcap_strerror(errno)); - break; + /* Select promiscuous mode on/off */ + +#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) { + 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, + PACKET_ADD_MEMBERSHIP, &mr, sizeof(mr)) == -1) + { + snprintf(ebuf, PCAP_ERRBUF_SIZE, + "setsockopt: %s", pcap_strerror(errno)); + break; + } } - - /* Compute the buffersize */ +#endif - 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; } while(0); - if( sock_fd != -1 ) - close( sock_fd ); + if (sock_fd != -1) + close(sock_fd); return 0; #else strncpy(ebuf, @@ -563,22 +1126,20 @@ live_open_new( pcap_t *handle, char *device, int promisc, #endif } -#ifdef HAVE_NETPACKET_PACKET_H +#ifdef HAVE_PF_PACKET_SOCKETS /* - iface_get_id: - - Return the index of the given device name. Fill ebuf and return - -1 on failure. -*/ + * Return the index of the given device name. Fill ebuf and return + * -1 on failure. + */ static int -iface_get_id( int fd, const char *device, char *ebuf ) +iface_get_id(int fd, const char *device, char *ebuf) { struct ifreq ifr; - memset( &ifr, 0, sizeof(ifr) ); - strncpy( ifr.ifr_name, device, sizeof(ifr.ifr_name) ); + memset(&ifr, 0, sizeof(ifr)); + strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); - if( ioctl(fd, SIOCGIFINDEX, &ifr) == -1 ) { + if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "ioctl: %s", pcap_strerror(errno)); return -1; @@ -588,21 +1149,19 @@ iface_get_id( int fd, const char *device, char *ebuf ) } /* - iface_bind: - - 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 ) +iface_bind(int fd, int ifindex, char *ebuf) { struct sockaddr_ll sll; - memset( &sll, 0, sizeof(sll) ); + memset(&sll, 0, sizeof(sll)); sll.sll_family = AF_PACKET; sll.sll_ifindex = ifindex; sll.sll_protocol = htons(ETH_P_ALL); - if( bind(fd, (struct sockaddr *) &sll, sizeof(sll)) == -1 ) { + if (bind(fd, (struct sockaddr *) &sll, sizeof(sll)) == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "bind: %s", pcap_strerror(errno)); return -1; @@ -616,53 +1175,124 @@ iface_bind( int fd, int ifindex, char *ebuf ) /* ===== Functions to interface to the older kernels ================== */ -/* With older kernels promiscuous mode is kind of interesting because we +/* + * 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. */ + * 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. + */ + +/* + * 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. + */ +static int did_atexit; + +static void pcap_close_all(void) +{ + struct pcap *handle; -struct ifreq restore_ifr; - /* Contains the device name and the interface flags to be restored - * at exit */ + while ((handle = pcaps_to_close) != NULL) + pcap_close(handle); +} -static void restore_interface( void ) +void pcap_close_linux( pcap_t *handle ) { - int status = socket(PF_INET, SOCK_PACKET, 0); + struct pcap *p, *prevp; + struct ifreq ifr; - if( status != -1 ) - status = ioctl(status, SIOCSIFFLAGS, &restore_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); } /* - live_open_old: - - Try to open a packet socket using the old kernel interface. - Returns 0 on failure. - FIXME: 0 uses to mean success (Sebastian) -*/ + * Try to open a packet socket using the old kernel interface. + * Returns 0 on failure. + * FIXME: 0 uses to mean success (Sebastian) + */ static int -live_open_old( pcap_t *handle, char *device, int promisc, - int to_ms, char *ebuf ) +live_open_old(pcap_t *handle, char *device, int promisc, + int to_ms, char *ebuf) { - int sock_fd = -1, mtu, arptype; + int sock_fd = -1, arptype; struct ifreq ifr; do { /* Open the socket */ - - sock_fd = socket( PF_INET, SOCK_PACKET, htons(ETH_P_ALL) ); - if( sock_fd == -1 ) { + + sock_fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL)); + if (sock_fd == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "socket: %s", pcap_strerror(errno)); break; @@ -671,95 +1301,128 @@ 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", + if (!device) { + 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(sock_fd, device, ebuf) == -1) break; /* Go to promisc mode */ - if( promisc ) { - memset( &ifr, 0, sizeof(ifr) ); - strncpy( ifr.ifr_name, device, sizeof(ifr.ifr_name) ); - if( ioctl(sock_fd, SIOCGIFFLAGS, &ifr) == -1 ) { + if (promisc) { + memset(&ifr, 0, sizeof(ifr)); + strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); + if (ioctl(sock_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; + if ((ifr.ifr_flags & IFF_PROMISC) == 0) { + /* + * 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; + } + } + ifr.ifr_flags |= IFF_PROMISC; - if( ioctl(sock_fd, SIOCSIFFLAGS, &ifr) == -1 ) { + if (ioctl(sock_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 ) + if (arptype == -1) break; + /* Save the socket FD in the pcap structure */ + 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 ) { + + /* + * 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. + */ + map_arphrd_to_dlt(handle, 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 ); + + } while (0); + + if (sock_fd != -1) + close(sock_fd); return 0; } /* - iface_bind_old: - - Bind the socket associated with FD to the given device using the - interface of the old kernels. -*/ + * 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 ) +iface_bind_old(int fd, const char *device, char *ebuf) { struct sockaddr saddr; - memset( &saddr, 0, sizeof(saddr) ); - strncpy( saddr.sa_data, device, sizeof(saddr.sa_data) ); - if( bind(fd, &saddr, sizeof(saddr)) == -1 ) { + memset(&saddr, 0, sizeof(saddr)); + strncpy(saddr.sa_data, device, sizeof(saddr.sa_data)); + if (bind(fd, &saddr, sizeof(saddr)) == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "bind: %s", pcap_strerror(errno)); return -1; @@ -772,19 +1435,20 @@ iface_bind_old( int fd, const char *device, char *ebuf ) /* ===== System calls available on all supported kernels ============== */ /* - iface_get_mtu: - - 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 ) +iface_get_mtu(int fd, const char *device, char *ebuf) { struct ifreq ifr; - memset( &ifr, 0, sizeof(ifr) ); - strncpy( ifr.ifr_name, device, sizeof(ifr.ifr_name) ); + if (!device) + return BIGGER_THAN_ALL_MTUS; - if( ioctl(fd, SIOCGIFMTU, &ifr) == -1 ) { + memset(&ifr, 0, sizeof(ifr)); + strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); + + if (ioctl(fd, SIOCGIFMTU, &ifr) == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "ioctl: %s", pcap_strerror(errno)); return -1; @@ -794,19 +1458,17 @@ iface_get_mtu( int fd, const char *device, char *ebuf ) } /* - iface_get_arptype: - - Get the hardware type of the given interface as ARPHRD_xxx constant. -*/ + * Get the hardware type of the given interface as ARPHRD_xxx constant. + */ static int -iface_get_arptype( int fd, const char *device, char *ebuf ) +iface_get_arptype(int fd, const char *device, char *ebuf) { struct ifreq ifr; - memset( &ifr, 0, sizeof(ifr) ); - strncpy( ifr.ifr_name, device, sizeof(ifr.ifr_name) ); + memset(&ifr, 0, sizeof(ifr)); + strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name)); - if( ioctl(fd, SIOCGIFHWADDR, &ifr) == -1 ) { + if (ioctl(fd, SIOCGIFHWADDR, &ifr) == -1) { snprintf(ebuf, PCAP_ERRBUF_SIZE, "ioctl: %s", pcap_strerror(errno)); return -1; @@ -815,3 +1477,232 @@ 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 we assume is 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) + ; + fcntl(handle->fd, F_SETFL, save_mode); + } + } + + /* + * 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