correct "protochain" processing.

diff --git a/gencode.c b/gencode.c
index 4534c401d496354011add758b23836fe15e44aaa..991f2fdcfbc2a0c8eee626d438eb09c7aae0318d 100644 (file)
--- a/gencode.c
+++ b/gencode.c
@@ -21,7 +21,7 @@
  */
 #ifndef lint
 static const char rcsid[] =
-    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.135 2000-10-30 06:06:53 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.136 2000-11-09 06:20:05 itojun Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -1857,7 +1857,6 @@ gen_protochain(v, proto, dir)
        int fix2, fix3, fix4, fix5;
        int ahcheck, again, end;
        int i, max;
-       int reg1 = alloc_reg();
        int reg2 = alloc_reg();
 
        memset(s, 0, sizeof(s));
@@ -1979,15 +1978,22 @@ gen_protochain(v, proto, dir)
 
                /*
                 * in short,
-                * A = P[X + 1];
-                * X = X + (P[X] + 1) * 8;
+                * A = P[X];
+                * X = X + (P[X + 1] + 1) * 8;
                 */
                /* A = X */
                s[i] = new_stmt(BPF_MISC|BPF_TXA);
                i++;
-               /* MEM[reg1] = A */
+               /* A = P[X + packet head] */
+               s[i] = new_stmt(BPF_LD|BPF_IND|BPF_B);
+               s[i]->s.k = off_nl;
+               i++;
+               /* MEM[reg2] = A */
                s[i] = new_stmt(BPF_ST);
-               s[i]->s.k = reg1;
+               s[i]->s.k = reg2;
+               i++;
+               /* A = X */
+               s[i] = new_stmt(BPF_MISC|BPF_TXA);
                i++;
                /* A += 1 */
                s[i] = new_stmt(BPF_ALU|BPF_ADD|BPF_K);
@@ -2000,18 +2006,6 @@ gen_protochain(v, proto, dir)
                s[i] = new_stmt(BPF_LD|BPF_IND|BPF_B);
                s[i]->s.k = off_nl;
                i++;
-               /* MEM[reg2] = A */
-               s[i] = new_stmt(BPF_ST);
-               s[i]->s.k = reg2;
-               i++;
-               /* X = MEM[reg1] */
-               s[i] = new_stmt(BPF_LDX|BPF_MEM);
-               s[i]->s.k = reg1;
-               i++;
-               /* A = P[X + packet head] */
-               s[i] = new_stmt(BPF_LD|BPF_IND|BPF_B);
-               s[i]->s.k = off_nl;
-               i++;
                /* A += 1 */
                s[i] = new_stmt(BPF_ALU|BPF_ADD|BPF_K);
                s[i]->s.k = 1;
@@ -2061,23 +2055,12 @@ gen_protochain(v, proto, dir)
 
        /*
         * in short,
-        * A = P[X + 1];
-        * X = X + (P[X] + 2) * 4;
+        * A = P[X];
+        * X = X + (P[X + 1] + 2) * 4;
         */
        /* A = X */
        s[i - 1]->s.jt = s[i] = new_stmt(BPF_MISC|BPF_TXA);
        i++;
-       /* MEM[reg1] = A */
-       s[i] = new_stmt(BPF_ST);
-       s[i]->s.k = reg1;
-       i++;
-       /* A += 1 */
-       s[i] = new_stmt(BPF_ALU|BPF_ADD|BPF_K);
-       s[i]->s.k = 1;
-       i++;
-       /* X = A */
-       s[i] = new_stmt(BPF_MISC|BPF_TAX);
-       i++;
        /* A = P[X + packet head]; */
        s[i] = new_stmt(BPF_LD|BPF_IND|BPF_B);
        s[i]->s.k = off_nl;
@@ -2086,9 +2069,15 @@ gen_protochain(v, proto, dir)
        s[i] = new_stmt(BPF_ST);
        s[i]->s.k = reg2;
        i++;
-       /* X = MEM[reg1] */
-       s[i] = new_stmt(BPF_LDX|BPF_MEM);
-       s[i]->s.k = reg1;
+       /* A = X */
+       s[i - 1]->s.jt = s[i] = new_stmt(BPF_MISC|BPF_TXA);
+       i++;
+       /* A += 1 */
+       s[i] = new_stmt(BPF_ALU|BPF_ADD|BPF_K);
+       s[i]->s.k = 1;
+       i++;
+       /* X = A */
+       s[i] = new_stmt(BPF_MISC|BPF_TAX);
        i++;
        /* A = P[X + packet head] */
        s[i] = new_stmt(BPF_LD|BPF_IND|BPF_B);
@@ -2139,7 +2128,6 @@ gen_protochain(v, proto, dir)
        b->stmts = s[1];        /*remember, s[0] is dummy*/
        b->s.k = v;
 
-       free_reg(reg1);
        free_reg(reg2);
 
        gen_and(b0, b);