From: itojun <itojun>
Date: Tue, 1 Aug 2000 17:36:49 +0000 (+0000)
Subject: udp header checksum.  from netbsd.
X-Git-Tag: tcpdump-3.5.1~190
X-Git-Url: https://git.tcpdump.org/tcpdump/commitdiff_plain/cb4e517e9aae83b3bc0beac4ad9fb9f2318a4dd2

udp header checksum.  from netbsd.
---

diff --git a/print-udp.c b/print-udp.c
index ef0266c3..11f60838 100644
--- a/print-udp.c
+++ b/print-udp.c
@@ -21,7 +21,7 @@
 
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/tcpdump/print-udp.c,v 1.75 2000-07-22 23:58:01 assar Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/tcpdump/print-udp.c,v 1.76 2000-08-01 17:36:49 itojun Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -292,6 +292,100 @@ 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;
+	union phu {
+		struct phdr {
+			u_int32_t src;
+			u_int32_t dst;
+			u_char mbz;
+			u_char proto;
+			u_int16_t len;
+		} ph;
+		u_int16_t pa[6];
+	} phu;
+	register const u_int16_t *sp;
+	u_int32_t sum;
+	tlen = ntohs(ip->ip_len) - ((const char *)up-(const char*)ip);
+
+	/* pseudo-header.. */
+	phu.ph.len = htons(tlen);
+	phu.ph.mbz = 0;
+	phu.ph.proto = IPPROTO_UDP;
+	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 *)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);
+}
+
+#ifdef INET6
+static int udp6_cksum(const struct ip6_hdr *ip6, const struct udphdr *up,
+	int len)
+{
+	int i, tlen;
+	register const u_int16_t *sp;
+	u_int32_t sum;
+	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;
+
+	tlen = ntohs(ip6->ip6_plen) + sizeof(struct ip6_hdr) -
+	    ((const char *)up - (const char*)ip6);
+
+	/* 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(tlen);
+	phu.ph.ph_nxt = IPPROTO_UDP;
+
+	sum = 0;
+	for (i = 0; i < sizeof(phu.pa) / sizeof(phu.pa[0]); i++)
+		sum += phu.pa[i];
+
+	sp = (const u_int16_t *)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);
+}
+#endif
+
+
 /* XXX probably should use getservbyname() and cache answers */
 #define TFTP_PORT 69		/*XXX*/
 #define KERBEROS_PORT 88	/*XXX*/
@@ -504,6 +598,32 @@ udp_print(register const u_char *bp, u_int length, register const u_char *bp2)
 	}
 #endif
 
+	if (ip->ip_v == 4 && vflag) {
+		int sum = up->uh_sum;
+		if (sum == 0) {
+			(void)printf(" [no cksum]");
+		} else if (TTEST2(cp[0], length)) {
+			sum = udp_cksum(ip, up, length);
+			if (sum != 0)
+				(void)printf(" [bad udp cksum %x!]", sum);
+			else
+				(void)printf(" [udp sum ok]");
+		}
+	}
+#ifdef INET6
+	if (ip->ip_v == 6 && ip6->ip6_plen && vflag) {
+		int sum = up->uh_sum;
+		/* for IPv6, UDP checksum is mandatory */
+		if (TTEST2(cp[0], length)) {
+			sum = udp6_cksum(ip6, up, length);
+			if (sum != 0)
+				(void)printf(" [bad udp cksum %x!]", sum);
+			else
+				(void)printf(" [udp sum ok]");
+		}
+	}
+#endif
+
 	if (!qflag) {
 #define ISPORT(p) (dport == (p) || sport == (p))
 		if (ISPORT(NAMESERVER_PORT))