Add a routine to do the "checksum with pseudo-header" stuff for IPv4.

Clean up some other stuff while we're at it.

Author: guyharris

ip.h

@@ -161,4 +161,4 @@ struct	ip_timestamp {
 #define	IP_MSS		576		/* default maximum segment size */
 
 /* in print-ip.c */
-extern u_int32_t ip_finddst(const struct ip *);
+extern int nextproto4_cksum(const struct ip *, const u_int8_t *, u_int, u_int);

netdissect.h

@@ -352,6 +352,7 @@ extern void igmp_print(netdissect_options *,
 		       register const u_char *, u_int);
 extern void igrp_print(netdissect_options *,const u_char *, u_int,
 		       const u_char *);
+extern int nextproto4_cksum(const struct ip *, const u_int8_t *, u_int, u_int);
 extern void ipN_print(netdissect_options *,const u_char *, u_int);
 extern void ipx_print(netdissect_options *,const u_char *, u_int);
 extern void isoclns_print(netdissect_options *,const u_char *,

print-dccp.c

@@ -60,7 +60,7 @@ static const char *dccp_feature_nums[] = {
 	"check data checksum",
 };
 
-static inline int dccp_csum_coverage(const struct dccp_hdr* dh, u_int len)
+static inline u_int dccp_csum_coverage(const struct dccp_hdr* dh, u_int len)
 {
 	u_int cov;
 
@@ -73,31 +73,8 @@ static inline int dccp_csum_coverage(const struct dccp_hdr* dh, u_int len)
 static int dccp_cksum(const struct ip *ip,
 	const struct dccp_hdr *dh, u_int len)
 {
-	int cov = dccp_csum_coverage(dh, len);
-	struct phdr {
-		u_int32_t src;
-		u_int32_t dst;
-		u_char mbz;
-		u_char proto;
-		u_int16_t len;
-	} ph;
-	struct cksum_vec vec[2];
-
-	/* pseudo-header.. */
-	ph.mbz = 0;
-	ph.len = htons(len);
-	ph.proto = IPPROTO_DCCP;
-	memcpy(&ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
-	if (IP_HL(ip) == 5)
-		memcpy(&ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
-	else
-		ph.dst = ip_finddst(ip);
-
-	vec[0].ptr = (const u_int8_t *)(void *)&ph;
-	vec[0].len = sizeof(ph);
-	vec[1].ptr = (const u_int8_t *)(void *)dh;
-	vec[1].len = cov;
-	return in_cksum(vec, 2);
+	return nextproto4_cksum(ip, (const u_int8_t *)(void *)dh,
+	    dccp_csum_coverage(dh, len), IPPROTO_DCCP);
 }
 
 #ifdef INET6

print-ip.c

@@ -87,7 +87,7 @@ ip_printroute(register const u_char *cp, u_int length)
  * This is used for UDP and TCP pseudo-header in the checksum
  * calculation.
  */
-u_int32_t
+static u_int32_t
 ip_finddst(const struct ip *ip)
 {
 	int length;
@@ -129,6 +129,39 @@ ip_finddst(const struct ip *ip)
 	return retval;
 }
 
+/*
+ * Compute a V4-style checksum by building a pseudoheader.
+ */
+int
+nextproto4_cksum(const struct ip *ip, const u_int8_t *data,
+		 u_int len, u_int next_proto)
+{
+	struct phdr {
+		u_int32_t src;
+		u_int32_t dst;
+		u_char mbz;
+		u_char proto;
+		u_int16_t len;
+	} ph;
+	struct cksum_vec vec[2];
+
+	/* pseudo-header.. */
+	ph.len = htons((u_int16_t)len);
+	ph.mbz = 0;
+	ph.proto = next_proto;
+	memcpy(&ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
+	if (IP_HL(ip) == 5)
+		memcpy(&ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
+	else
+		ph.dst = ip_finddst(ip);
+
+	vec[0].ptr = (const u_int8_t *)(void *)&ph;
+	vec[0].len = sizeof(ph);
+	vec[1].ptr = data;
+	vec[1].len = len;
+	return (in_cksum(vec, 2));
+}
+
 static void
 ip_printts(register const u_char *cp, u_int length)
 {

print-tcp.c

@@ -129,30 +129,8 @@ static int tcp_cksum(register const struct ip *ip,
 		     register const struct tcphdr *tp,
 		     register u_int len)
 {
-        struct phdr {
-                u_int32_t src;
-                u_int32_t dst;
-                u_char mbz;
-                u_char proto;
-                u_int16_t len;
-        } ph;
-        struct cksum_vec vec[2];
-
-        /* pseudo-header.. */
-        ph.len = htons((u_int16_t)len);
-        ph.mbz = 0;
-        ph.proto = IPPROTO_TCP;
-        memcpy(&ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
-        if (IP_HL(ip) == 5)
-                memcpy(&ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
-        else
-                ph.dst = ip_finddst(ip);
-
-        vec[0].ptr = (const u_int8_t *)(void *)&ph;
-        vec[0].len = sizeof(ph);
-        vec[1].ptr = (const u_int8_t *)tp;
-        vec[1].len = len;
-        return in_cksum(vec, 2);
+	return (nextproto4_cksum(ip, (const u_int8_t *)tp, len,
+	    IPPROTO_TCP));
 }
 
 void

print-udp.c

@@ -286,30 +286,8 @@ static int udp_cksum(register const struct ip *ip,
 		     register const struct udphdr *up,
 		     register u_int len)
 {
-	struct phdr {
-		u_int32_t src;
-		u_int32_t dst;
-		u_char mbz;
-		u_char proto;
-		u_int16_t len;
-	} ph;
-	struct cksum_vec vec[2];
-
-	/* pseudo-header.. */
-	ph.len = htons((u_int16_t)len);
-	ph.mbz = 0;
-	ph.proto = IPPROTO_UDP;
-	memcpy(&ph.src, &ip->ip_src.s_addr, sizeof(u_int32_t));
-	if (IP_HL(ip) == 5)
-		memcpy(&ph.dst, &ip->ip_dst.s_addr, sizeof(u_int32_t));
-	else
-		ph.dst = ip_finddst(ip);
-
-	vec[0].ptr = (const u_int8_t *)(void *)&ph;
-	vec[0].len = sizeof(ph);
-	vec[1].ptr = (const u_int8_t *)(void *)up;
-	vec[1].len = len;
-	return (in_cksum(vec, 2));
+	return (nextproto4_cksum(ip, (const u_int8_t *)(void *)up, len,
+	    IPPROTO_UDP));
 }
 
 #ifdef INET6