Let tcpdump detect bad ICMP checksums with the -v flag.

Tested on amd64, i386, loongson, and macppc.

OK florian@

diff --git a/usr.sbin/tcpdump/print-icmp.c b/usr.sbin/tcpdump/print-icmp.c
index a554c0a..fcb51f4 100644 (file)
--- a/usr.sbin/tcpdump/print-icmp.c
+++ b/usr.sbin/tcpdump/print-icmp.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: print-icmp.c,v 1.21 2014/01/11 04:35:52 lteo Exp $    */
+/*     $OpenBSD: print-icmp.c,v 1.22 2014/01/11 04:40:45 lteo Exp $    */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1991, 1993, 1994, 1995, 1996
@@ -373,7 +373,17 @@ icmp_print(const u_char *bp, u_int length, const u_char *bp2)
                str = tok2str(icmp2str, "type-#%u", dp->icmp_type);
                break;
        }
-        (void)printf("icmp: %s", str);
+       (void)printf("icmp: %s", str);
+       if (vflag) {
+               u_int16_t sum;
+               if (TTEST2(dp->icmp_type, length)) {
+                       sum = in_cksum((const u_short *)dp, length, 0);
+                       if (sum != 0)
+                               (void)printf(" [bad icmp cksum %x!]", sum);
+                       else
+                               (void)printf(" [icmp cksum ok]");
+               }
+    }
        if (vflag > 1 && !ICMP_INFOTYPE(dp->icmp_type) &&
            TTEST(dp->icmp_ip)) {
                (void)printf(" for ");