DVMRP: Modernize packet parsing style.

Remove all ND_TCHECK*() instances as redundant. Remove all improvised
snapshot end guards. Make invalid packet handling uniform and always
print the reason. Merge trivial single-use helper functions into the
code that needs them. Add more length checks. Use tok2str() to print the
message type. Lose a single-use variable in print_probe().

diff --git a/print-dvmrp.c b/print-dvmrp.c
index 1ce7022d6a78ddb4e271ef055c81c10eaab34f48..7d7ca07555acf323e53d319be8b1ddf2965e05c5 100644 (file)
--- a/print-dvmrp.c
+++ b/print-dvmrp.c
@@ -47,6 +47,18 @@
 #define DVMRP_PRUNE            7       /* prune message */
 #define DVMRP_GRAFT            8       /* graft message */
 #define DVMRP_GRAFT_ACK                9       /* graft acknowledgement */
+static const struct tok dvmrp_msgtype_str[] = {
+       { DVMRP_PROBE,          "Probe"              },
+       { DVMRP_REPORT,         "Report"             },
+       { DVMRP_ASK_NEIGHBORS,  "Ask-neighbors(old)" },
+       { DVMRP_NEIGHBORS,      "Neighbors(old)"     },
+       { DVMRP_ASK_NEIGHBORS2, "Ask-neighbors2"     },
+       { DVMRP_NEIGHBORS2,     "Neighbors2"         },
+       { DVMRP_PRUNE,          "Prune"              },
+       { DVMRP_GRAFT,          "Graft"              },
+       { DVMRP_GRAFT_ACK,      "Graft-ACK"          },
+       { 0, NULL }
+};
 
 /*
  * 'flags' byte values in DVMRP_NEIGHBORS2 reply.
@@ -57,26 +69,23 @@
 #define DVMRP_NF_DISABLED      0x20    /* administratively disabled */
 #define DVMRP_NF_QUERIER       0x40    /* I am the subnet's querier */
 
-static int print_probe(netdissect_options *, const u_char *, const u_char *, u_int);
-static int print_report(netdissect_options *, const u_char *, const u_char *, u_int);
-static int print_neighbors(netdissect_options *, const u_char *, const u_char *, u_int);
-static int print_neighbors2(netdissect_options *, const u_char *, const u_char *, u_int, uint8_t, uint8_t);
-static int print_prune(netdissect_options *, const u_char *);
-static int print_graft(netdissect_options *, const u_char *);
-static int print_graft_ack(netdissect_options *, const u_char *);
+static void print_probe(netdissect_options *, const u_char *, u_int);
+static void print_report(netdissect_options *, const u_char *, u_int);
+static void print_neighbors(netdissect_options *, const u_char *, u_int);
+static void print_neighbors2(netdissect_options *, const u_char *, u_int, uint8_t, uint8_t);
 
 void
 dvmrp_print(netdissect_options *ndo,
             const u_char *bp, u_int len)
 {
-       const u_char *ep;
        u_char type;
        uint8_t major_version, minor_version;
 
        ndo->ndo_protocol = "dvmrp";
-       ep = ndo->ndo_snapend;
-       if (bp >= ep)
-               return;
+       if (len < 8) {
+               ND_PRINT(" [length %u < 8]", len);
+               goto invalid;
+       }
 
        type = GET_U_1(bp + 1);
 
@@ -84,40 +93,26 @@ dvmrp_print(netdissect_options *ndo,
        bp += 8;
        len -= 8;
 
+       ND_PRINT(" %s", tok2str(dvmrp_msgtype_str, "[type %u]", type));
        switch (type) {
 
        case DVMRP_PROBE:
-               ND_PRINT(" Probe");
                if (ndo->ndo_vflag) {
-                       if (print_probe(ndo, bp, ep, len) < 0)
-                               goto trunc;
+                       print_probe(ndo, bp, len);
                }
                break;
 
        case DVMRP_REPORT:
-               ND_PRINT(" Report");
                if (ndo->ndo_vflag > 1) {
-                       if (print_report(ndo, bp, ep, len) < 0)
-                               goto trunc;
+                       print_report(ndo, bp, len);
                }
                break;
 
-       case DVMRP_ASK_NEIGHBORS:
-               ND_PRINT(" Ask-neighbors(old)");
-               break;
-
        case DVMRP_NEIGHBORS:
-               ND_PRINT(" Neighbors(old)");
-               if (print_neighbors(ndo, bp, ep, len) < 0)
-                       goto trunc;
-               break;
-
-       case DVMRP_ASK_NEIGHBORS2:
-               ND_PRINT(" Ask-neighbors2");
+               print_neighbors(ndo, bp, len);
                break;
 
        case DVMRP_NEIGHBORS2:
-               ND_PRINT(" Neighbors2");
                /*
                 * extract version from IGMP group address field
                 */
@@ -125,42 +120,32 @@ dvmrp_print(netdissect_options *ndo,
                major_version = GET_U_1(bp + 3);
                minor_version = GET_U_1(bp + 2);
                bp += 4;
-               if (print_neighbors2(ndo, bp, ep, len, major_version,
-                   minor_version) < 0)
-                       goto trunc;
+               print_neighbors2(ndo, bp, len, major_version, minor_version);
                break;
 
        case DVMRP_PRUNE:
-               ND_PRINT(" Prune");
-               if (print_prune(ndo, bp) < 0)
-                       goto trunc;
+               ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
+               ND_PRINT(" timer ");
+               unsigned_relts_print(ndo, GET_BE_U_4(bp + 8));
                break;
 
        case DVMRP_GRAFT:
-               ND_PRINT(" Graft");
-               if (print_graft(ndo, bp) < 0)
-                       goto trunc;
+               ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
                break;
 
        case DVMRP_GRAFT_ACK:
-               ND_PRINT(" Graft-ACK");
-               if (print_graft_ack(ndo, bp) < 0)
-                       goto trunc;
-               break;
-
-       default:
-               ND_PRINT(" [type %u]", type);
+               ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
                break;
        }
        return;
 
-trunc:
-       nd_print_trunc(ndo);
+invalid:
+       nd_print_invalid(ndo);
 }
 
-static int
+static void
 print_report(netdissect_options *ndo,
-             const u_char *bp, const u_char *ep,
+             const u_char *bp,
              u_int len)
 {
        uint32_t mask, origin;
@@ -169,8 +154,8 @@ print_report(netdissect_options *ndo,
 
        while (len > 0) {
                if (len < 3) {
-                       ND_PRINT(" [|]");
-                       return (0);
+                       ND_PRINT(" [length %u < 3]", len);
+                       goto invalid;
                }
                mask = (uint32_t)0xff << 24 | GET_U_1(bp) << 16 |
                        GET_U_1(bp + 1) << 8 | GET_U_1(bp + 2);
@@ -186,13 +171,9 @@ print_report(netdissect_options *ndo,
                bp += 3;
                len -= 3;
                do {
-                       if (bp + width + 1 > ep) {
-                               ND_PRINT(" [|]");
-                               return (0);
-                       }
                        if (len < width + 1) {
                                ND_PRINT("\n\t  [Truncated Report]");
-                               return (0);
+                               goto invalid;
                        }
                        origin = 0;
                        for (i = 0; i < width; ++i) {
@@ -211,41 +192,45 @@ print_report(netdissect_options *ndo,
                        len -= width + 1;
                } while (!done);
        }
-       return (0);
+       return;
+
+invalid:
+       nd_print_invalid(ndo);
 }
 
-static int
+static void
 print_probe(netdissect_options *ndo,
-            const u_char *bp, const u_char *ep,
+            const u_char *bp,
             u_int len)
 {
-       uint32_t genid;
-
-       ND_TCHECK_4(bp);
-       if ((len < 4) || ((bp + 4) > ep)) {
-               ND_PRINT(" [|}");
-               return (0);
+       if (len < 4) {
+               ND_PRINT(" [full length %u < 4]", len);
+               goto invalid;
        }
-       genid = GET_BE_U_4(bp);
-       bp += 4;
-       len -= 4;
        ND_PRINT(ndo->ndo_vflag > 1 ? "\n\t" : " ");
-       ND_PRINT("genid %u", genid);
+       ND_PRINT("genid %u", GET_BE_U_4(bp));
        if (ndo->ndo_vflag < 2)
-               return (0);
+               return;
 
-       while ((len > 0) && (bp < ep)) {
+       bp += 4;
+       len -= 4;
+       while (len > 0) {
+               if (len < 4) {
+                       ND_PRINT("[remaining length %u < 4]", len);
+                       goto invalid;
+               }
                ND_PRINT("\n\tneighbor %s", GET_IPADDR_STRING(bp));
                bp += 4; len -= 4;
        }
-       return (0);
-trunc:
-       return (-1);
+       return;
+
+invalid:
+       nd_print_invalid(ndo);
 }
 
-static int
+static void
 print_neighbors(netdissect_options *ndo,
-                const u_char *bp, const u_char *ep,
+                const u_char *bp,
                 u_int len)
 {
        const u_char *laddr;
@@ -253,8 +238,11 @@ print_neighbors(netdissect_options *ndo,
        u_char thresh;
        int ncount;
 
-       while (len > 0 && bp < ep) {
-               ND_TCHECK_7(bp);
+       while (len > 0) {
+               if (len < 7) {
+                       ND_PRINT(" [length %u < 7]", len);
+                       goto invalid;
+               }
                laddr = bp;
                bp += 4;
                metric = GET_U_1(bp);
@@ -265,6 +253,10 @@ print_neighbors(netdissect_options *ndo,
                bp++;
                len -= 7;
                while (--ncount >= 0) {
+                       if (len < 4) {
+                               ND_PRINT(" [length %u < 4]", len);
+                               goto invalid;
+                       }
                        ND_PRINT(" [%s ->", GET_IPADDR_STRING(laddr));
                        ND_PRINT(" %s, (%u/%u)]",
                                   GET_IPADDR_STRING(bp), metric, thresh);
@@ -272,14 +264,15 @@ print_neighbors(netdissect_options *ndo,
                        len -= 4;
                }
        }
-       return (0);
-trunc:
-       return (-1);
+       return;
+
+invalid:
+       nd_print_invalid(ndo);
 }
 
-static int
+static void
 print_neighbors2(netdissect_options *ndo,
-                 const u_char *bp, const u_char *ep,
+                 const u_char *bp,
                  u_int len, uint8_t major_version,
                  uint8_t minor_version)
 {
@@ -289,8 +282,11 @@ print_neighbors2(netdissect_options *ndo,
 
        ND_PRINT(" (v %u.%u):", major_version, minor_version);
 
-       while (len > 0 && bp < ep) {
-               ND_TCHECK_8(bp);
+       while (len > 0) {
+               if (len < 8) {
+                       ND_PRINT(" [length %u < 8]", len);
+                       goto invalid;
+               }
                laddr = bp;
                bp += 4;
                metric = GET_U_1(bp);
@@ -302,7 +298,11 @@ print_neighbors2(netdissect_options *ndo,
                ncount = GET_U_1(bp);
                bp++;
                len -= 8;
-               while (--ncount >= 0 && (len >= 4) && (bp + 4) <= ep) {
+               while (--ncount >= 0 && len > 0) {
+                       if (len < 4) {
+                               ND_PRINT(" [length %u < 4]", len);
+                               goto invalid;
+                       }
                        ND_PRINT(" [%s -> ", GET_IPADDR_STRING(laddr));
                        ND_PRINT("%s (%u/%u", GET_IPADDR_STRING(bp),
                                     metric, thresh);
@@ -321,38 +321,12 @@ print_neighbors2(netdissect_options *ndo,
                        len -= 4;
                }
                if (ncount != -1) {
-                       ND_PRINT(" [|]");
-                       return (0);
+                       ND_PRINT(" [invalid ncount]");
+                       goto invalid;
                }
        }
-       return (0);
-trunc:
-       return (-1);
-}
-
-static int
-print_prune(netdissect_options *ndo,
-            const u_char *bp)
-{
-       ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
-       bp += 8;
-       ND_PRINT(" timer ");
-       unsigned_relts_print(ndo, GET_BE_U_4(bp));
-       return (0);
-}
-
-static int
-print_graft(netdissect_options *ndo,
-            const u_char *bp)
-{
-       ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
-       return (0);
-}
+       return;
 
-static int
-print_graft_ack(netdissect_options *ndo,
-                const u_char *bp)
-{
-       ND_PRINT(" src %s grp %s", GET_IPADDR_STRING(bp), GET_IPADDR_STRING(bp + 4));
-       return (0);
+invalid:
+       nd_print_invalid(ndo);
 }