Add routines to generate code to load values relative to the beginning

of the link-layer, network-layer, and transport-layer (assuming the
network layer is IPv4) headers.  This makes it a bit clearer what stuff
would be changed for variable-length link-layer headers or
variable-length pseudo-headers before the link-layer header.

diff --git a/gencode.c b/gencode.c
index cbe6a5c37ed592c513247abdc32b1f5898b0f688..5bb8e9884b20ff5be5d8fd7611205908f193e6aa 100644 (file)
--- a/gencode.c
+++ b/gencode.c
@@ -21,7 +21,7 @@
  */
 #ifndef lint
 static const char rcsid[] _U_ =
-    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.221.2.8 2005-04-25 18:59:20 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.221.2.9 2005-05-01 00:38:34 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -163,6 +163,9 @@ static struct block *gen_mcmp(u_int, u_int, bpf_int32, bpf_u_int32);
 static struct block *gen_bcmp(u_int, u_int, const u_char *);
 static struct block *gen_ncmp(bpf_u_int32, bpf_u_int32, bpf_u_int32,
     bpf_u_int32, bpf_u_int32, int);
+static struct slist *gen_load_llrel(u_int, u_int);
+static struct slist *gen_load_nlrel(u_int, u_int);
+static struct slist *gen_load_ipv4tlrel(u_int, u_int);
 static struct block *gen_uncond(int);
 static inline struct block *gen_true(void);
 static inline struct block *gen_false(void);
@@ -496,8 +499,7 @@ gen_cmp(offset, size, v)
        struct slist *s;
        struct block *b;
 
-       s = new_stmt(BPF_LD|BPF_ABS|size);
-       s->s.k = offset;
+       s = gen_load_llrel(offset, size);
 
        b = new_block(JMP(BPF_JEQ));
        b->stmts = s;
@@ -514,8 +516,7 @@ gen_cmp_gt(offset, size, v)
        struct slist *s;
        struct block *b;
 
-       s = new_stmt(BPF_LD|BPF_ABS|size);
-       s->s.k = offset;
+       s = gen_load_llrel(offset, size);
 
        b = new_block(JMP(BPF_JGT));
        b->stmts = s;
@@ -1067,6 +1068,58 @@ init_linktype(p)
        /* NOTREACHED */
 }
 
+/*
+ * Load a value relative to the beginning of the link-layer header.
+ */
+static struct slist *
+gen_load_llrel(offset, size)
+       u_int offset, size;
+{
+       struct slist *s;
+
+       s = new_stmt(BPF_LD|BPF_ABS|size);
+       s->s.k = offset;
+       return s;
+}
+
+/*
+ * Load a value relative to the beginning of the network-layer header.
+ */
+static struct slist *
+gen_load_nlrel(offset, size)
+       u_int offset, size;
+{
+       return gen_load_llrel(off_nl + offset, size);
+}
+
+/*
+ * Load a value relative to the beginning of the transport-layer header,
+ * where the network-layer header is an IPv4 header.  (This doesn't handle
+ * AH headers.)
+ */
+static struct slist *
+gen_load_ipv4tlrel(offset, size)
+       u_int offset, size;
+{
+       struct slist *s;
+
+       /*
+        * Load the X register with the length of the IPv4 header,
+        * in bytes.
+        */
+       s = new_stmt(BPF_LDX|BPF_MSH|BPF_B);
+       s->s.k = off_nl;
+
+       /*
+        * Load the item at {length of the link-layer header} + {length
+        * of the IPv4 header} + {specified offset}.
+        */
+       s->next = new_stmt(BPF_LD|BPF_IND|size);
+       s->next->s.k = off_nl + offset;
+
+       return s;
+}
+
 static struct block *
 gen_uncond(rsense)
        int rsense;
@@ -2246,8 +2299,7 @@ gen_wlanhostop(eaddr, dir)
                 *
                 * First, check for To DS set, i.e. check "link[1] & 0x01".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 1;
+               s = gen_load_llrel(1, BPF_B);
                b1 = new_block(JMP(BPF_JSET));
                b1->s.k = 0x01; /* To DS */
                b1->stmts = s;
@@ -2262,8 +2314,7 @@ gen_wlanhostop(eaddr, dir)
                 * Now, check for To DS not set, i.e. check
                 * "!(link[1] & 0x01)".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 1;
+               s = gen_load_llrel(1, BPF_B);
                b2 = new_block(JMP(BPF_JSET));
                b2->s.k = 0x01; /* To DS */
                b2->stmts = s;
@@ -2286,8 +2337,7 @@ gen_wlanhostop(eaddr, dir)
                 * Now check for From DS being set, and AND that with
                 * the ORed-together checks.
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 1;
+               s = gen_load_llrel(1, BPF_B);
                b1 = new_block(JMP(BPF_JSET));
                b1->s.k = 0x02; /* From DS */
                b1->stmts = s;
@@ -2296,8 +2346,7 @@ gen_wlanhostop(eaddr, dir)
                /*
                 * Now check for data frames with From DS not set.
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 1;
+               s = gen_load_llrel(1, BPF_B);
                b2 = new_block(JMP(BPF_JSET));
                b2->s.k = 0x02; /* From DS */
                b2->stmts = s;
@@ -2320,8 +2369,7 @@ gen_wlanhostop(eaddr, dir)
                 * Now check for a data frame.
                 * I.e, check "link[0] & 0x08".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 0;
+               gen_load_llrel(0, BPF_B);
                b1 = new_block(JMP(BPF_JSET));
                b1->s.k = 0x08;
                b1->stmts = s;
@@ -2336,8 +2384,7 @@ gen_wlanhostop(eaddr, dir)
                 * is a management frame.
                 * I.e, check "!(link[0] & 0x08)".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 0;
+               s = gen_load_llrel(0, BPF_B);
                b2 = new_block(JMP(BPF_JSET));
                b2->s.k = 0x08;
                b2->stmts = s;
@@ -2364,8 +2411,7 @@ gen_wlanhostop(eaddr, dir)
                 *
                 * I.e., check "!(link[0] & 0x04)".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 0;
+               s = gen_load_llrel(0, BPF_B);
                b1 = new_block(JMP(BPF_JSET));
                b1->s.k = 0x04;
                b1->stmts = s;
@@ -2400,8 +2446,7 @@ gen_wlanhostop(eaddr, dir)
                 *
                 * First, check for To DS set, i.e. "link[1] & 0x01".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 1;
+               s = gen_load_llrel(1, BPF_B);
                b1 = new_block(JMP(BPF_JSET));
                b1->s.k = 0x01; /* To DS */
                b1->stmts = s;
@@ -2416,8 +2461,7 @@ gen_wlanhostop(eaddr, dir)
                 * Now, check for To DS not set, i.e. check
                 * "!(link[1] & 0x01)".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 1;
+               s = gen_load_llrel(1, BPF_B);
                b2 = new_block(JMP(BPF_JSET));
                b2->s.k = 0x01; /* To DS */
                b2->stmts = s;
@@ -2439,8 +2483,7 @@ gen_wlanhostop(eaddr, dir)
                 * Now check for a data frame.
                 * I.e, check "link[0] & 0x08".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 0;
+               s = gen_load_llrel(0, BPF_B);
                b1 = new_block(JMP(BPF_JSET));
                b1->s.k = 0x08;
                b1->stmts = s;
@@ -2455,8 +2498,7 @@ gen_wlanhostop(eaddr, dir)
                 * is a management frame.
                 * I.e, check "!(link[0] & 0x08)".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 0;
+               s = gen_load_llrel(0, BPF_B);
                b2 = new_block(JMP(BPF_JSET));
                b2->s.k = 0x08;
                b2->stmts = s;
@@ -2483,8 +2525,7 @@ gen_wlanhostop(eaddr, dir)
                 *
                 * I.e., check "!(link[0] & 0x04)".
                 */
-               s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-               s->s.k = 0;
+               s = gen_load_llrel(0, BPF_B);
                b1 = new_block(JMP(BPF_JSET));
                b1->s.k = 0x04;
                b1->stmts = s;
@@ -3180,8 +3221,7 @@ gen_ipfrag()
        struct block *b;
 
        /* not ip frag */
-       s = new_stmt(BPF_LD|BPF_H|BPF_ABS);
-       s->s.k = off_nl + 6;
+       s = gen_load_nlrel(6, BPF_H);
        b = new_block(JMP(BPF_JSET));
        b->s.k = 0x1fff;
        b->stmts = s;
@@ -3198,11 +3238,7 @@ gen_portatom(off, v)
        struct slist *s;
        struct block *b;
 
-       s = new_stmt(BPF_LDX|BPF_MSH|BPF_B);
-       s->s.k = off_nl;
-
-       s->next = new_stmt(BPF_LD|BPF_IND|BPF_H);
-       s->next->s.k = off_nl + off;
+       s = gen_load_ipv4tlrel(off, BPF_H);
 
        b = new_block(JMP(BPF_JEQ));
        b->stmts = s;
@@ -3404,21 +3440,14 @@ gen_portrangeatom(off, v1, v2)
                v1 = v2;
                v2 = vtemp;
        }
-       s1 = new_stmt(BPF_LDX|BPF_MSH|BPF_B);
-       s1->s.k = off_nl;
 
-       s1->next = new_stmt(BPF_LD|BPF_IND|BPF_H);
-       s1->next->s.k = off_nl + off;
+       s1 = gen_load_ipv4tlrel(off, BPF_H);
 
        b1 = new_block(JMP(BPF_JGE));
        b1->stmts = s1;
        b1->s.k = v1;
 
-       s2 = new_stmt(BPF_LDX|BPF_MSH|BPF_B);
-       s2->s.k = off_nl;
-
-       s2->next = new_stmt(BPF_LD|BPF_IND|BPF_H);
-       s2->next->s.k = off_nl + off;
+       s2 = gen_load_ipv4tlrel(off, BPF_H);
 
        b2 = new_block(JMP(BPF_JGT));
        gen_not(b2);
@@ -3526,15 +3555,13 @@ gen_portrangeatom6(off, v1, v2)
                v2 = vtemp;
        }
 
-       s1 = new_stmt(BPF_LD|BPF_ABS|BPF_H);
-       s1->s.k = off_nl + 40 + off;
+       s1 = gen_load_nlrel(40 + off, BPF_H);
 
        b1 = new_block(JMP(BPF_JGE));
        b1->stmts = s1;
        b1->s.k = v1;
 
-       s2 = new_stmt(BPF_LD|BPF_ABS|BPF_H);
-       s2->s.k = off_nl + 40 + off;
+       s2 = gen_load_nlrel(40 + off, BPF_H);
 
        b2 = new_block(JMP(BPF_JGT));
        gen_not(b2);
@@ -5205,8 +5232,7 @@ gen_mac_multicast(offset)
        register struct slist *s;
 
        /* link[offset] & 1 != 0 */
-       s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-       s->s.k = offset;
+       s = gen_load_llrel(offset, BPF_B);
        b0 = new_block(JMP(BPF_JSET));
        b0->s.k = 1;
        b0->stmts = s;
@@ -5270,8 +5296,7 @@ gen_multicast(proto)
                         *
                         * First, check for To DS set, i.e. "link[1] & 0x01".
                         */
-                       s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-                       s->s.k = 1;
+                       s = gen_load_llrel(1, BPF_B);
                        b1 = new_block(JMP(BPF_JSET));
                        b1->s.k = 0x01; /* To DS */
                        b1->stmts = s;
@@ -5286,8 +5311,7 @@ gen_multicast(proto)
                         * Now, check for To DS not set, i.e. check
                         * "!(link[1] & 0x01)".
                         */
-                       s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-                       s->s.k = 1;
+                       s = gen_load_llrel(1, BPF_B);
                        b2 = new_block(JMP(BPF_JSET));
                        b2->s.k = 0x01; /* To DS */
                        b2->stmts = s;
@@ -5309,8 +5333,7 @@ gen_multicast(proto)
                         * Now check for a data frame.
                         * I.e, check "link[0] & 0x08".
                         */
-                       s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-                       s->s.k = 0;
+                       s = gen_load_llrel(0, BPF_B);
                        b1 = new_block(JMP(BPF_JSET));
                        b1->s.k = 0x08;
                        b1->stmts = s;
@@ -5325,8 +5348,7 @@ gen_multicast(proto)
                         * is a management frame.
                         * I.e, check "!(link[0] & 0x08)".
                         */
-                       s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-                       s->s.k = 0;
+                       s = gen_load_llrel(0, BPF_B);
                        b2 = new_block(JMP(BPF_JSET));
                        b2->s.k = 0x08;
                        b2->stmts = s;
@@ -5353,8 +5375,7 @@ gen_multicast(proto)
                         *
                         * I.e., check "!(link[0] & 0x04)".
                         */
-                       s = new_stmt(BPF_LD|BPF_B|BPF_ABS);
-                       s->s.k = 0;
+                       s = gen_load_llrel(0, BPF_B);
                        b1 = new_block(JMP(BPF_JSET));
                        b1->s.k = 0x04;
                        b1->stmts = s;