Let tcpdump detect bad ICMPv6 checksums with the -v flag.

Tested on amd64, i386, loongson, and macppc.

OK florian@

diff --git a/usr.sbin/tcpdump/print-icmp6.c b/usr.sbin/tcpdump/print-icmp6.c
index 229ab4b..0249039 100644 (file)
--- a/usr.sbin/tcpdump/print-icmp6.c
+++ b/usr.sbin/tcpdump/print-icmp6.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: print-icmp6.c,v 1.11 2013/10/24 09:33:22 deraadt Exp $        */
+/*     $OpenBSD: print-icmp6.c,v 1.12 2014/01/11 04:41:08 lteo Exp $   */
 
 /*
  * Copyright (c) 1988, 1989, 1990, 1991, 1993, 1994
@@ -45,6 +45,7 @@
 #include <arpa/inet.h>
 
 #include <stdio.h>
+#include <string.h>
 
 #include <netinet/ip6.h>
 #include <netinet/icmp6.h>
@@ -92,6 +93,36 @@ static struct tok mldv2report2str[] = {
 #define MLDV2_QQIC_FLOAT               (1 << 7)
 #define MLDV2_QQI(mant, exp)   ((mant | 0x10) << (exp + 3))
 
+static int
+icmp6_cksum(const struct ip6_hdr *ip6, const struct icmp6_hdr *icmp6,
+    u_int len)
+{
+       union {
+               struct {
+                       struct in6_addr ph_src;
+                       struct in6_addr ph_dst;
+                       u_int32_t       ph_len;
+                       u_int8_t        ph_zero[3];
+                       u_int8_t        ph_nxt;
+               } ph;
+               u_int16_t pa[20];
+       } phu;
+       size_t i;
+       u_int32_t sum = 0;
+
+       /* pseudo-header */
+       memset(&phu, 0, sizeof(phu));
+       phu.ph.ph_src = ip6->ip6_src;
+       phu.ph.ph_dst = ip6->ip6_dst;
+       phu.ph.ph_len = htonl(len);
+       phu.ph.ph_nxt = IPPROTO_ICMPV6;
+
+       for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
+               sum += phu.pa[i];
+
+       return in_cksum((u_short *)icmp6, len, sum);
+}
+
 void
 icmp6_print(const u_char *bp, u_int length, const u_char *bp2)
 {
@@ -453,6 +484,16 @@ icmp6_print(const u_char *bp, u_int length, const u_char *bp2)
                printf("icmp6: type-#%d", dp->icmp6_type);
                break;
        }
+       if (vflag) {
+               u_int16_t sum;
+               if (TTEST2(dp->icmp6_type, length)) {
+                       sum = icmp6_cksum(ip, dp, length);
+                       if (sum != 0)
+                               printf(" [bad icmp6 cksum %x!]", sum);
+                       else
+                               printf(" [icmp6 cksum ok]");
+               }
+       }
        return;
 trunc:
        fputs("[|icmp6]", stdout);