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Double-check tcp/udp checksum if we get enough data to do it.

This commit is contained in:
sommerfe 1998-12-18 20:28:54 +00:00
parent 3bd57bb34b
commit 4b41ddc197
2 changed files with 115 additions and 4 deletions
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58
usr.sbin/tcpdump/print-tcp.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: print-tcp.c,v 1.9 1997/10/03 20:38:03 christos Exp $ */
/* $NetBSD: print-tcp.c,v 1.10 1998/12/18 20:28:54 sommerfe Exp $ */
/*
* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
@ -27,7 +27,7 @@
static const char rcsid[] =
"@(#) Header: print-tcp.c,v 1.55 97/06/15 13:20:28 leres Exp (LBL)";
#else
__RCSID("$NetBSD: print-tcp.c,v 1.9 1997/10/03 20:38:03 christos Exp $");
__RCSID("$NetBSD: print-tcp.c,v 1.10 1998/12/18 20:28:54 sommerfe Exp $");
#endif
#endif
@ -105,6 +105,48 @@ struct tcp_seq_hash {
static struct tcp_seq_hash tcp_seq_hash[TSEQ_HASHSIZE];
static int tcp_cksum(register const struct ip *ip,
register const struct tcphdr *tp,
register int len)
{
int i, tlen;
struct phdr {
u_long src;
u_long dst;
u_char mbz;
u_char proto;
u_short len;
} ph;
register const u_short *sp;
int sum;
tlen = ntohs(ip->ip_len) - ((const char *)tp-(const char*)ip);
/* pseudo-header.. */
ph.len = htons(tlen);
ph.mbz = 0;
ph.proto = ip->ip_p;
ph.src = ip->ip_src.s_addr;
ph.dst = ip->ip_dst.s_addr;
sp = (const u_short *)&ph;
sum = sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5];
sp = (const u_short *)tp;
for (i=0; i<(tlen&~1); i+= 2)
sum += *sp++;
if (tlen & 1) {
sum += htons( (*(const char *)sp) << 8);
}
while (sum > 0xffff)
sum = (sum & 0xffff) + (sum >> 16);
sum = ~sum & 0xffff;
return (sum);
}
void
tcp_print(register const u_char *bp, register u_int length,
@ -229,6 +271,18 @@ tcp_print(register const u_char *bp, register u_int length,
(void)printf(" [bad hdr length]");
return;
}
if (vflag) {
int sum;
if (TTEST2(tp->th_sport, length)) {
sum = tcp_cksum(ip, tp, length);
if (sum != 0)
(void)printf(" [bad tcp cksum %x!]", sum);
else
(void)printf(" [tcp sum ok]");
}
}
length -= hlen;
if (length > 0 || flags & (TH_SYN | TH_FIN | TH_RST))
(void)printf(" %lu:%lu(%d)", (long) seq, (long) (seq + length),

61
usr.sbin/tcpdump/print-udp.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: print-udp.c,v 1.6 1997/10/03 19:55:50 christos Exp $ */
/* $NetBSD: print-udp.c,v 1.7 1998/12/18 20:28:54 sommerfe Exp $ */
/*
* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
@ -27,7 +27,7 @@
static const char rcsid[] =
"@(#) Header: print-udp.c,v 1.60 97/07/27 21:58:48 leres Exp (LBL)";
#else
__RCSID("$NetBSD: print-udp.c,v 1.6 1997/10/03 19:55:50 christos Exp $");
__RCSID("$NetBSD: print-udp.c,v 1.7 1998/12/18 20:28:54 sommerfe Exp $");
#endif
#endif
@ -291,6 +291,50 @@ rtcp_print(const u_char *hdr, const u_char *ep)
return (hdr + len);
}
static int udp_cksum(register const struct ip *ip,
register const struct udphdr *up,
register int len)
{
int i, tlen;
struct phdr {
u_long src;
u_long dst;
u_char mbz;
u_char proto;
u_short len;
} ph;
register const u_short *sp;
int sum;
tlen = ntohs(ip->ip_len) - ((const char *)up-(const char*)ip);
/* pseudo-header.. */
ph.len = htons(tlen);
ph.mbz = 0;
ph.proto = ip->ip_p;
ph.src = ip->ip_src.s_addr;
ph.dst = ip->ip_dst.s_addr;
sp = (const u_short *)&ph;
sum = sp[0]+sp[1]+sp[2]+sp[3]+sp[4]+sp[5];
sp = (const u_short *)up;
for (i=0; i<(tlen&~1); i+= 2)
sum += *sp++;
if (tlen & 1) {
sum += htons( (*(const char *)sp) << 8);
}
while (sum > 0xffff)
sum = (sum & 0xffff) + (sum >> 16);
sum = ~sum & 0xffff;
return (sum);
}
/* XXX probably should use getservbyname() and cache answers */
#define TFTP_PORT 69 /*XXX*/
#define KERBEROS_PORT 88 /*XXX*/
@ -422,6 +466,19 @@ udp_print(register const u_char *bp, u_int length, register const u_char *bp2)
ipaddr_string(&ip->ip_src), udpport_string(sport),
ipaddr_string(&ip->ip_dst), udpport_string(dport));
if (vflag) {
int sum = up->uh_sum;
if (sum == 0) {
(void)printf(" [no cksum]");
} else if (TTEST2(up->uh_sport, length)) {
sum = udp_cksum(ip, up, length);
if (sum != 0)
(void)printf(" [bad udp cksum %x!]", sum);
else
(void)printf(" [udp sum ok]");
}
}
if (!qflag) {
#define ISPORT(p) (dport == (p) || sport == (p))
if (ISPORT(NAMESERVER_PORT))