Use the passed in length instead of the IP header's length in the

[tcpdump] / print-tcp.c

diff --git a/print-tcp.c b/print-tcp.c
index ce1fc9aaec75b2213fa3071ecce71dd3a020941d..54ae3d5571c6d7dff716625f0188baab98d009a5 100644 (file)
--- a/print-tcp.c
+++ b/print-tcp.c
@@ -21,7 +21,7 @@
 
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.87 2001-06-25 21:38:50 itojun Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/tcpdump/print-tcp.c,v 1.88 2001-08-20 17:53:53 fenner Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -104,7 +104,6 @@ static int tcp_cksum(register const struct ip *ip,
                     register const struct tcphdr *tp,
                     register int len)
 {
-       int i, tlen;
        union phu {
                struct phdr {
                        u_int32_t src;
@@ -115,34 +114,18 @@ static int tcp_cksum(register const struct ip *ip,
                } ph;
                u_int16_t pa[6];
        } phu;
-       register const u_int16_t *sp;
-       u_int32_t sum;
-       tlen = ntohs(ip->ip_len) - ((const char *)tp-(const char*)ip);
+       const u_int16_t *sp;
 
        /* pseudo-header.. */
-       phu.ph.len = htons(tlen);
+       phu.ph.len = htons(len);        /* XXX */
        phu.ph.mbz = 0;
        phu.ph.proto = IPPROTO_TCP;
        memcpy(&phu.ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
        memcpy(&phu.ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
 
        sp = &phu.pa[0];
-       sum = sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5];
-
-       sp = (const u_int16_t *)tp;
-
-       for (i=0; i<(tlen&~1); i+= 2)
-               sum += *sp++;
-
-       if (tlen & 1) {
-               sum += htons( (*(const u_int8_t *)sp) << 8);
-       }
-
-       while (sum > 0xffff)
-               sum = (sum & 0xffff) + (sum >> 16);
-       sum = ~sum & 0xffff;
-
-       return (sum);
+       return in_cksum((u_short *)tp, len,
+                       sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5]);
 }
 
 #ifdef INET6