From Koryn Grant:
The DAG 4.2 OC-48 cards (and revisions thereof) produce ERF records that do not contain the trailing FCS. However, pcap-dag.c assumed that there is an FCS and strips the final word of the packet. This meant that packets captured with libpcap on a DAG 4.2 are truncated by four bytes, unless a magical environment variable (ERF_FCS_BITS) was set. This patch autodetects when the DAG card is a 4.2, and turns off the FCS-stripping feature so that packets are no longer truncated. Also, include "dagnew.h" and "dagapi.h" with quotes, not angle brackets, as they should be in the user search path, not the system search path.
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pcap-dag.c
19
pcap-dag.c
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@ -15,7 +15,7 @@
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#ifndef lint
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static const char rcsid[] _U_ =
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"@(#) $Header: /tcpdump/master/libpcap/pcap-dag.c,v 1.19 2004-11-10 09:28:25 guy Exp $ (LBL)";
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"@(#) $Header: /tcpdump/master/libpcap/pcap-dag.c,v 1.20 2005-01-21 10:11:39 guy Exp $ (LBL)";
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#endif
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#ifdef HAVE_CONFIG_H
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@ -41,8 +41,8 @@ struct mbuf; /* Squelch compiler warnings on some platforms for */
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struct rtentry; /* declarations in <net/if.h> */
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#include <net/if.h>
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#include <dagnew.h>
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#include <dagapi.h>
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#include "dagnew.h"
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#include "dagapi.h"
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#define MIN_DAG_SNAPLEN 12
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#define MAX_DAG_SNAPLEN 2040
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@ -385,6 +385,7 @@ dag_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebu
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pcap_t *handle;
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char *s;
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int n;
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daginf_t* daginf;
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if (device == NULL) {
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snprintf(ebuf, PCAP_ERRBUF_SIZE, "device is NULL: %s", pcap_strerror(errno));
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@ -454,9 +455,17 @@ dag_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebu
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*/
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handle->md.dag_mem_bottom = 0;
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handle->md.dag_mem_top = 0;
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/* TODO: query the card */
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handle->md.dag_fcs_bits = 32;
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/* Query the card first for special cases. */
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daginf = dag_info(handle->fd);
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if ((0x4200 == daginf->device_code) || (0x4230 == daginf->device_code))
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{
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/* DAG 4.2S and 4.23S already strip the FCS. Stripping the final word again truncates the packet. */
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handle->md.dag_fcs_bits = 0;
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}
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/* Then allow an environment variable to override. */
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if ((s = getenv("ERF_FCS_BITS")) != NULL) {
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if ((n = atoi(s)) == 0 || n == 16|| n == 32) {
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handle->md.dag_fcs_bits = n;
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