*/
#ifndef lint
static const char rcsid[] =
- "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.37 2000-10-25 06:59:10 guy Exp $ (LBL)";
+ "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.38 2000-10-25 07:46:50 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'd have to catch "pcap_close()"
+ * and restore the value the promiscuous flag had when we opened
+ * the device - which may not be the value it should have, if
+ * another socket also requested promiscuous mode between the time
+ * when we opened the socket and the time when we close the socket.
+ * We currently just punt, printing a warning and hinting that the
+ * user should upgrade to a 2.2 or later kernel.
*/
static int
pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
{
+#ifdef HAVE_NETPACKET_PACKET_H
+ struct sockaddr_ll from;
+#else
struct sockaddr from;
+#endif
socklen_t fromlen;
int packet_len, caplen;
struct pcap_pkthdr pcap_header;
}
}
+#ifdef HAVE_NETPACKET_PACKET_H
+ /*
+ * 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
+
/*
* XXX: According to the kernel source we should get the real
* packet len if calling recvfrom with MSG_TRUNC set. It does
/* It seems the kernel supports the new interface. */
handle->md.sock_packet = 0;
+ /*
+ * 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);
+
/*
* What kind of frames do we have to deal with? Fall back
* to cooked mode if we have an unknown interface type.
if (arptype == -1)
break;
handle->linktype = map_arphrd_to_dlt(arptype);
- } else
- handle->linktype = DLT_RAW;
-
- if (handle->linktype == -1) {
- /* Unknown interface type - reopen in cooked mode */
+ 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));
+ 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;
+ }
- if (close(sock_fd) == -1) {
- snprintf(ebuf, PCAP_ERRBUF_SIZE,
- "close: %s", pcap_strerror(errno));
- break;
+ fprintf(stderr,
+ "Warning: arptype %d not supported by "
+ "libpcap - falling back to cooked "
+ "socket\n",
+ arptype);
+ handle->linktype = DLT_RAW;
}
- 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;
- }
-
- if (device) {
device_id = iface_get_id(sock_fd, device, ebuf);
if (device_id == -1)
break;
if (iface_bind(sock_fd, device_id, ebuf) == -1)
break;
+ } else {
+ handle->linktype = DLT_RAW;
+
+ /*
+ * 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;
}
/* Select promiscuous mode on/off */
projects / libpcap / commitdiff
