X-Git-Url: https://git.tcpdump.org/tcpdump/blobdiff_plain/38700c7f24646dfbc6ac0ed529d3ed727c545cd0..61c422a88caefe986c2bc0a7f2f3028f696fa5cd:/print-vjc.c

diff --git a/print-vjc.c b/print-vjc.c
index fc7aafa9..b5f88ab6 100644
--- a/print-vjc.c
+++ b/print-vjc.c
@@ -19,13 +19,18 @@
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  */
 
+/* \summary: PPP Van Jacobson compression printer */
+
+/* specification: RFC 1144 */
+
 #ifdef HAVE_CONFIG_H
 #include "config.h"
 #endif
 
-#include <tcpdump-stdinc.h>
+#include <netdissect-stdinc.h>
 
-#include "interface.h"
+#include "netdissect.h"
+#include "extract.h"
 #include "slcompress.h"
 #include "ppp.h"
 
@@ -70,9 +75,16 @@
  * We therefore leave "proto" - which is the PPP protocol type - in place,
  * *not* marked as unused, for now, so that GCC warnings about the
  * unused argument remind us that we should fix this some day.
+ *
+ * XXX - also, it fetches the TCP checksum field in COMPRESSED_TCP
+ * packets directly, rather than with EXTRACT_BE_U_2(); RFC 1144 says
+ * it's "the unmodified TCP checksum", which would imply that it's
+ * big-endian, but perhaps, on the platform where this was developed,
+ * the packets were munged by the networking stack before being handed
+ * to the packet capture mechanism.
  */
 int
-vjc_print(netdissect_options *ndo, register const char *bp, u_short proto _U_)
+vjc_print(netdissect_options *ndo, register const u_char *bp, u_short proto _U_)
 {
 	int i;
 
@@ -89,13 +101,13 @@ vjc_print(netdissect_options *ndo, register const char *bp, u_short proto _U_)
 		if (ndo->ndo_eflag)
 			ND_PRINT((ndo, "(vjc type=compressed TCP) "));
 		for (i = 0; i < 8; i++) {
-			if (bp[1] & (0x80 >> i))
+			if (EXTRACT_U_1(bp + 1) & (0x80 >> i))
 				ND_PRINT((ndo, "%c", "?CI?SAWU"[i]));
 		}
-		if (bp[1])
+		if (EXTRACT_U_1(bp + 1))
 			ND_PRINT((ndo, " "));
 		ND_PRINT((ndo, "C=0x%02x ", bp[2]));
-		ND_PRINT((ndo, "sum=0x%04x ", *(u_short *)&bp[3]));
+		ND_PRINT((ndo, "sum=0x%04x ", *(const u_short *)(bp + 3)));
 		return -1;
 	case TYPE_ERROR:
 		if (ndo->ndo_eflag)