From 2dd3e0acd6d7e40d046113d562efea81b876f6fd Mon Sep 17 00:00:00 2001
From: guy <guy>
Date: Fri, 21 Jan 2005 10:11:39 +0000
Subject: [PATCH] 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.
---
 pcap-dag.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/pcap-dag.c b/pcap-dag.c
index d1ec5b9..03ba11a 100644
--- a/pcap-dag.c
+++ b/pcap-dag.c
@@ -15,7 +15,7 @@
 
 #ifndef lint
 static const char rcsid[] _U_ =
-	"@(#) $Header: /tcpdump/master/libpcap/pcap-dag.c,v 1.19 2004-11-10 09:28:25 guy Exp $ (LBL)";
+	"@(#) $Header: /tcpdump/master/libpcap/pcap-dag.c,v 1.20 2005-01-21 10:11:39 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -41,8 +41,8 @@ struct mbuf;		/* Squelch compiler warnings on some platforms for */
 struct rtentry;		/* declarations in <net/if.h> */
 #include <net/if.h>
 
-#include <dagnew.h>
-#include <dagapi.h>
+#include "dagnew.h"
+#include "dagapi.h"
 
 #define MIN_DAG_SNAPLEN		12
 #define MAX_DAG_SNAPLEN		2040
@@ -385,6 +385,7 @@ dag_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebu
 	pcap_t *handle;
 	char *s;
 	int n;
+	daginf_t* daginf;
 	
 	if (device == NULL) {
 		snprintf(ebuf, PCAP_ERRBUF_SIZE, "device is NULL: %s", pcap_strerror(errno));
@@ -454,9 +455,17 @@ dag_open_live(const char *device, int snaplen, int promisc, int to_ms, char *ebu
 	 */
 	handle->md.dag_mem_bottom = 0;
 	handle->md.dag_mem_top = 0;
-
-	/* TODO: query the card */
 	handle->md.dag_fcs_bits = 32;
+
+	/* Query the card first for special cases. */
+	daginf = dag_info(handle->fd);
+	if ((0x4200 == daginf->device_code) || (0x4230 == daginf->device_code))
+	{
+		/* DAG 4.2S and 4.23S already strip the FCS.  Stripping the final word again truncates the packet. */
+		handle->md.dag_fcs_bits = 0;
+	}
+
+	/* Then allow an environment variable to override. */
 	if ((s = getenv("ERF_FCS_BITS")) != NULL) {
 		if ((n = atoi(s)) == 0 || n == 16|| n == 32) {
 			handle->md.dag_fcs_bits = n;