UDP: Modernize packet parsing style.

Remove all ND_TCHECK_*() instances as redundant. Remove or convert a few
improvised snapshot end guards. Reduce arity of rtcp_print(). Test the
AppleTalk LAP type after testing the UDP port numbers, not before.

diff --git a/CHANGES b/CHANGES
index a5e9a31a627c900ca4b98dd6736727b0156b57a5..630a9deec551a4b60a1450de209c82fe58c8fca9 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -2,7 +2,7 @@ Monthday, Month DD, YYYY by gharris and denis
   Summary for 5.0.0 tcpdump release (so far!)
     Source code:
       Use %zu when printing a sizeof to squelch compiler warnings
-      BOOTP, EGP, EIGRP, Geneve, L2TP, OLSR, PGM, RSVP: Modernize packet parsing style
+      BOOTP, EGP, EIGRP, Geneve, L2TP, OLSR, PGM, RSVP, UDP: Modernize packet parsing style
       EGP: Replace custom code with tok2str()
       EIGRP: Get the packet header fields right.
       UDP: Clean up address and port printing.

diff --git a/print-udp.c b/print-udp.c
index ad0c47b0b4e9ae5203c3d7fdfd83ce817a6c74c9..b315f1e77fea6fb8faf57a9dba45d10579415556 100644 (file)
--- a/print-udp.c
+++ b/print-udp.c
@@ -212,7 +212,7 @@ rtp_print(netdissect_options *ndo, const u_char *hdr, u_int len)
 }
 
 static const u_char *
-rtcp_print(netdissect_options *ndo, const u_char *hdr, const u_char *ep)
+rtcp_print(netdissect_options *ndo, const u_char *hdr)
 {
        /* rtp v2 control (rtcp) */
        const struct rtcp_rr *rr = 0;
@@ -220,16 +220,15 @@ rtcp_print(netdissect_options *ndo, const u_char *hdr, const u_char *ep)
        const struct rtcphdr *rh = (const struct rtcphdr *)hdr;
        u_int len;
        uint16_t flags;
+       uint32_t ssrc;
        u_int cnt;
        double ts, dts;
 
        ndo->ndo_protocol = "rtcp";
-       if ((const u_char *)(rh + 1) > ep)
-               goto trunc;
-       ND_TCHECK_SIZE(rh);
        len = (GET_BE_U_2(rh->rh_len) + 1) * 4;
        flags = GET_BE_U_2(rh->rh_flags);
        cnt = (flags >> 8) & 0x1f;
+       ssrc = GET_BE_U_4(rh->rh_ssrc);
        switch (flags & 0xff) {
        case RTCP_PT_SR:
                sr = (const struct rtcp_sr *)(rh + 1);
@@ -237,10 +236,7 @@ rtcp_print(netdissect_options *ndo, const u_char *hdr, const u_char *ep)
                if (len != cnt * sizeof(*rr) + sizeof(*sr) + sizeof(*rh))
                        ND_PRINT(" [%u]", len);
                if (ndo->ndo_vflag)
-                       ND_PRINT(" %u", GET_BE_U_4(rh->rh_ssrc));
-               if ((const u_char *)(sr + 1) > ep)
-                       goto trunc;
-               ND_TCHECK_SIZE(sr);
+                       ND_PRINT(" %u", ssrc);
                ts = (double)(GET_BE_U_4(sr->sr_ntp.upper)) +
                    ((double)(GET_BE_U_4(sr->sr_ntp.lower)) /
                     FMAXINT);
@@ -254,18 +250,18 @@ rtcp_print(netdissect_options *ndo, const u_char *hdr, const u_char *ep)
                        ND_PRINT(" [%u]", len);
                rr = (const struct rtcp_rr *)(rh + 1);
                if (ndo->ndo_vflag)
-                       ND_PRINT(" %u", GET_BE_U_4(rh->rh_ssrc));
+                       ND_PRINT(" %u", ssrc);
                break;
        case RTCP_PT_SDES:
                ND_PRINT(" sdes %u", len);
                if (ndo->ndo_vflag)
-                       ND_PRINT(" %u", GET_BE_U_4(rh->rh_ssrc));
+                       ND_PRINT(" %u", ssrc);
                cnt = 0;
                break;
        case RTCP_PT_BYE:
                ND_PRINT(" bye %u", len);
                if (ndo->ndo_vflag)
-                       ND_PRINT(" %u", GET_BE_U_4(rh->rh_ssrc));
+                       ND_PRINT(" %u", ssrc);
                cnt = 0;
                break;
        default:
@@ -276,9 +272,6 @@ rtcp_print(netdissect_options *ndo, const u_char *hdr, const u_char *ep)
        if (cnt > 1)
                ND_PRINT(" c%u", cnt);
        while (cnt != 0) {
-               if ((const u_char *)(rr + 1) > ep)
-                       goto trunc;
-               ND_TCHECK_SIZE(rr);
                if (ndo->ndo_vflag)
                        ND_PRINT(" %u", GET_BE_U_4(rr->rr_srcid));
                ts = (double)(GET_BE_U_4(rr->rr_lsr)) / 65536.;
@@ -290,10 +283,6 @@ rtcp_print(netdissect_options *ndo, const u_char *hdr, const u_char *ep)
                cnt--;
        }
        return (hdr + len);
-
-trunc:
-       nd_print_trunc(ndo);
-       return ep;
 }
 
 static uint16_t udp_cksum(netdissect_options *ndo, const struct ip *ip,
@@ -360,6 +349,7 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
        const u_char *ep = ndo->ndo_snapend;
        uint16_t sport, dport;
        u_int ulen;
+       uint16_t udp_sum;
        const struct ip6_hdr *ip6;
 
        ndo->ndo_protocol = "udp";
@@ -371,7 +361,7 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
                ip6 = NULL;
        if (!ND_TTEST_2(up->uh_dport)) {
                udpipaddr_noport_print(ndo, ip);
-               goto trunc;
+               nd_trunc_longjmp(ndo);
        }
 
        sport = GET_BE_U_2(up->uh_sport);
@@ -380,13 +370,11 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
                udpipaddr_print(ndo, ip, sport, dport);
 
        if (length < sizeof(struct udphdr)) {
-               ND_PRINT("truncated-udp %u", length);
-               return;
-       }
-       if (!ND_TTEST_2(up->uh_ulen)) {
-               goto trunc;
+               ND_PRINT("undersized-udp %u", length);
+               goto invalid;
        }
        ulen = GET_BE_U_2(up->uh_ulen);
+       udp_sum = GET_BE_U_2(up->uh_sum);
        /*
         * IPv6 Jumbo Datagrams; see RFC 2675.
         * If the length is zero, and the length provided to us is
@@ -395,8 +383,8 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
        if (ulen == 0 && length > 65535)
                ulen = length;
        if (ulen < sizeof(struct udphdr)) {
-               ND_PRINT("truncated-udplength %u", ulen);
-               return;
+               ND_PRINT("undersized-udplength %u", ulen);
+               goto invalid;
        }
        ulen -= sizeof(struct udphdr);
        length -= sizeof(struct udphdr);
@@ -404,9 +392,6 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
                length = ulen;
 
        cp = (const u_char *)(up + 1);
-       if (cp > ndo->ndo_snapend) {
-               goto trunc;
-       }
 
        if (ndo->ndo_packettype) {
                const struct sunrpc_msg *rp;
@@ -439,7 +424,7 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
 
                case PT_RTCP:
                        while (cp < ep)
-                               cp = rtcp_print(ndo, cp, ep);
+                               cp = rtcp_print(ndo, cp);
                        break;
 
                case PT_SNMP:
@@ -520,14 +505,13 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
 
        if (ndo->ndo_vflag && !ndo->ndo_Kflag && !fragmented) {
                /* Check the checksum, if possible. */
-               uint16_t sum, udp_sum;
+               uint16_t sum;
 
                /*
                 * XXX - do this even if vflag == 1?
                 * TCP does, and we do so for UDP-over-IPv6.
                 */
                if (IP_V(ip) == 4 && (ndo->ndo_vflag > 1)) {
-                       udp_sum = GET_BE_U_2(up->uh_sum);
                        if (udp_sum == 0) {
                                ND_PRINT("[no cksum] ");
                        } else if (ND_TTEST_LEN(cp, length)) {
@@ -545,7 +529,6 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
                        /* for IPv6, UDP checksum is mandatory */
                        if (ND_TTEST_LEN(cp, length)) {
                                sum = udp6_cksum(ndo, ip6, up, length + sizeof(struct udphdr));
-                               udp_sum = GET_BE_U_2(up->uh_sum);
 
                                if (sum != 0) {
                                        ND_PRINT("[bad udp cksum 0x%04x -> 0x%04x!] ",
@@ -679,9 +662,8 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
                        zep_print(ndo, cp, length);
                else if (IS_SRC_OR_DST_PORT(MPLS_PORT))
                        mpls_print(ndo, cp, length);
-               else if (ND_TTEST_1(((const struct LAP *)cp)->type) &&
-                        GET_U_1(((const struct LAP *)cp)->type) == lapDDP &&
-                        (atalk_port(sport) || atalk_port(dport))) {
+               else if ((atalk_port(sport) || atalk_port(dport)) &&
+                        GET_U_1(((const struct LAP *)cp)->type) == lapDDP) {
                        if (ndo->ndo_vflag)
                                ND_PRINT("kip ");
                        llap_print(ndo, cp, length);
@@ -706,6 +688,6 @@ udp_print(netdissect_options *ndo, const u_char *bp, u_int length,
        }
        return;
 
-trunc:
-       nd_print_trunc(ndo);
+invalid:
+       nd_print_invalid(ndo);
 }