*/
#ifndef lint
static const char rcsid[] =
- "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.61 2001-07-29 18:25:47 guy Exp $ (LBL)";
+ "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.62 2001-08-23 16:36:41 guy Exp $ (LBL)";
#endif
/*
pcap_t *
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));
+ handle = malloc(sizeof(*handle));
if (handle == NULL) {
snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
pcap_strerror(errno));
return NULL;
}
+ /* Compute the buffersize */
+
+ 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;
+
+ /* 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;
+ }
+
+ /*
+ * If we're using SOCKET_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.
+ *
+ * That's 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.
+ */
+ handle->md.readlen = handle->bufsize;
+ } 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->md.readlen = handle->snapshot;
+ }
+
return handle;
}
int to_ms, char *ebuf)
{
#ifdef HAVE_PF_PACKET_SOCKETS
- int sock_fd = -1, device_id, mtu, arptype;
+ int sock_fd = -1, device_id, arptype;
struct packet_mreq mr;
/* One shot loop used for error handling - bail out with 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->buffer = malloc(handle->bufsize + handle->offset);
- if (!handle->buffer) {
- snprintf(ebuf, PCAP_ERRBUF_SIZE,
- "malloc: %s", pcap_strerror(errno));
- break;
- }
-
- /*
- * This is a 2.2 or later kernel, as it has PF_PACKET;
- * "recvfrom()", when passed the MSG_TRUNC flag, will
- * return the actual length of the packet, not the
- * number of bytes from the packet copied to userland,
- * so we can safely pass it a byte count based on the
- * snapshot length.
- */
- handle->md.readlen = handle->snapshot;
return 1;
} while(0);
live_open_old(pcap_t *handle, char *device, int promisc,
int to_ms, char *ebuf)
{
- int sock_fd = -1, mtu, arptype;
- struct utsname utsname;
+ int sock_fd = -1, arptype;
struct ifreq ifr;
do {
}
}
- /* Compute the buffersize */
-
- mtu = iface_get_mtu(sock_fd, device, ebuf);
- if (mtu == -1)
- break;
- handle->bufsize = MAX_LINKHEADER_SIZE + mtu;
- if (handle->bufsize < handle->snapshot)
- handle->bufsize = handle->snapshot;
-
/* All done - fill in the pcap handle */
arptype = iface_get_arptype(sock_fd, device, ebuf);
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->fd = sock_fd;
-
/*
* XXX - handle ISDN types here? We can't fall back on
* cooked sockets, so we'd have to figure out from the
"interface type of %s not supported", device);
break;
}
- handle->buffer = malloc(handle->bufsize + handle->offset);
- if (!handle->buffer) {
- snprintf(ebuf, PCAP_ERRBUF_SIZE,
- "malloc: %s", pcap_strerror(errno));
- break;
- }
- /*
- * This might be a 2.0[.x] kernel - check.
- */
- if (uname(&utsname) < 0 ||
- strncmp(utsname.release, "2.0", 3) == 0) {
- /*
- * 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.
- *
- * 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.
- */
- handle->md.readlen = handle->bufsize;
- } else {
- /*
- * This is a 2.2[.x] or later kernel (although
- * why we're using SOCK_PACKET on such a system
- * is unknown to me).
- *
- * We can safely pass "recvfrom()" a byte count
- * based on the snapshot length.
- */
- handle->md.readlen = handle->snapshot;
- }
return 1;
} while (0);
projects / libpcap / commitdiff
