Eliminate some unneeded variables and move some comments.

Eliminate orig_linktype; we were setting it but never using it.

Eliminnte orig_nl; we were setting it, but in the only places where we
were using it, it had the same value as off_nl, so just use off_nl.

Move some comments next to the code to which they're actually referring
(don't speak of changing offsets before we actually change the offsets).

diff --git a/gencode.c b/gencode.c
index c2ce8b7359254a6d3039974f1af0924cb6a3656c..38db34b7db83f45da3c124cc78db795b0ac02905 100644 (file)
--- a/gencode.c
+++ b/gencode.c
@@ -129,11 +129,11 @@
 static jmp_buf top_ctx;
 static pcap_t *bpf_pcap;
 
-/* Hack for updating VLAN, MPLS, and PPPoE offsets. */
+/* Hack for handling VLAN and MPLS stacks. */
 #ifdef WIN32
-static u_int   orig_linktype = (u_int)-1, orig_nl = (u_int)-1, label_stack_depth = (u_int)-1, vlan_stack_depth = (u_int)-1;
+static u_int   label_stack_depth = (u_int)-1, vlan_stack_depth = (u_int)-1;
 #else
-static u_int   orig_linktype = -1U, orig_nl = -1U, label_stack_depth = -1U, vlan_stack_depth = -1U;
+static u_int   label_stack_depth = -1U, vlan_stack_depth = -1U;
 #endif
 
 /* XXX */
@@ -960,8 +960,6 @@ init_linktype(p)
        off_macpl = 0;
        off_macpl_is_variable = 0;
 
-       orig_linktype = -1;
-       orig_nl = -1;
         label_stack_depth = 0;
         vlan_stack_depth = 0;
 
@@ -8149,8 +8147,6 @@ gen_vlan(vlan_num)
         * be done assuming a VLAN, even though the "or" could be viewed
         * as meaning "or, if this isn't a VLAN packet...".
         */
-       orig_nl = off_nl;
-
        switch (linktype) {
 
        case DLT_EN10MB:
@@ -8189,26 +8185,13 @@ gen_mpls(label_num)
 {
        struct  block   *b0, *b1;
 
-       /*
-        * Change the offsets to point to the type and data fields within
-        * the MPLS packet.  Just increment the offsets, so that we
-        * can support a hierarchy, e.g. "mpls 100000 && mpls 1024" to
-        * capture packets with an outer label of 100000 and an inner
-        * label of 1024.
-        *
-        * XXX - this is a bit of a kludge.  See comments in gen_vlan().
-        */
-        orig_nl = off_nl;
-
         if (label_stack_depth > 0) {
             /* just match the bottom-of-stack bit clear */
-            b0 = gen_mcmp(OR_MACPL, orig_nl-2, BPF_B, 0, 0x01);
+            b0 = gen_mcmp(OR_MACPL, off_nl-2, BPF_B, 0, 0x01);
         } else {
             /*
-             * Indicate that we're checking MPLS-encapsulated headers,
-             * to make sure higher level code generators don't try to
-             * match against IP-related protocols such as Q_ARP, Q_RARP
-             * etc.
+             * We're not in an MPLS stack yet, so check the link-layer
+             * type against MPLS.
              */
             switch (linktype) {
 
@@ -8239,12 +8222,26 @@ gen_mpls(label_num)
        /* If a specific MPLS label is requested, check it */
        if (label_num >= 0) {
                label_num = label_num << 12; /* label is shifted 12 bits on the wire */
-               b1 = gen_mcmp(OR_MACPL, orig_nl, BPF_W, (bpf_int32)label_num,
+               b1 = gen_mcmp(OR_MACPL, off_nl, BPF_W, (bpf_int32)label_num,
                    0xfffff000); /* only compare the first 20 bits */
                gen_and(b0, b1);
                b0 = b1;
        }
 
+        /*
+         * Change the offsets to point to the type and data fields within
+         * the MPLS packet.  Just increment the offsets, so that we
+         * can support a hierarchy, e.g. "mpls 100000 && mpls 1024" to
+         * capture packets with an outer label of 100000 and an inner
+         * label of 1024.
+         *
+         * Increment the MPLS stack depth as well; this indicates that
+         * we're checking MPLS-encapsulated headers, to make sure higher
+         * level code generators don't try to match against IP-related
+         * protocols such as Q_ARP, Q_RARP etc.
+         *
+         * XXX - this is a bit of a kludge.  See comments in gen_vlan().
+         */
         off_nl_nosnap += 4;
         off_nl += 4;
         label_stack_depth++;
@@ -8272,6 +8269,16 @@ gen_pppoes(sess_num)
         */
        b0 = gen_linktype((bpf_int32)ETHERTYPE_PPPOES);
 
+       /* If a specific session is requested, check PPPoE session id */
+       if (sess_num >= 0) {
+               b1 = gen_mcmp(OR_MACPL, off_nl, BPF_W,
+                   (bpf_int32)sess_num, 0x0000ffff);
+               gen_and(b0, b1);
+               b0 = b1;
+       }
+
+       is_pppoes = 1;
+
        /*
         * Change the offsets to point to the type and data fields within
         * the PPP packet, and note that this is PPPoE rather than
@@ -8300,20 +8307,7 @@ gen_pppoes(sess_num)
         * as all the "or ..." tests would be done assuming PPPoE, even
         * though the "or" could be viewed as meaning "or, if this isn't
         * a PPPoE packet...".
-        */
-       orig_linktype = off_linktype;   /* save original values */
-       orig_nl = off_nl;
-       is_pppoes = 1;
-
-       /* If a specific session is requested, check PPPoE session id */
-       if (sess_num >= 0) {
-               b1 = gen_mcmp(OR_MACPL, orig_nl, BPF_W,
-                   (bpf_int32)sess_num, 0x0000ffff);
-               gen_and(b0, b1);
-               b0 = b1;
-       }
-
-       /*
+        *
         * The "network-layer" protocol is PPPoE, which has a 6-byte
         * PPPoE header, followed by a PPP packet.
         *