Do the DLT_PPI per-packet DLT check before computing any of the

variable-length offsets.

Update some routine names and comments.

diff --git a/gencode.c b/gencode.c
index 9842a5848e4776bfd9b048d217857c9ac11c5905..dbce58dfe76495ceb79dc61b8b5365dd0c31a03c 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 1.290.2.8 2007-11-06 19:09:31 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.290.2.9 2007-11-07 19:33:00 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -202,7 +202,7 @@ static struct block *gen_ether_linktype(int);
 static struct block *gen_linux_sll_linktype(int);
 static struct slist *gen_load_radiotap_llprefixlen(void);
 static struct slist *gen_load_ppi_llprefixlen(void);
-static void insert_load_llprefixlen(struct block *);
+static void insert_compute_vloffsets(struct block *);
 static struct slist *gen_llprefixlen(void);
 static struct slist *gen_off_macpl(void);
 static int ethertype_to_ppptype(int);
@@ -496,18 +496,6 @@ finish_parse(p)
        struct block *p;
 {
        struct block *ppi_dlt_check;
-       
-       ppi_dlt_check = gen_ppi_dlt_check();
-
-       if (ppi_dlt_check != NULL)
-       {
-               gen_and(ppi_dlt_check, p);
-       }
-
-       backpatch(p, gen_retblk(snaplen));
-       p->sense = !p->sense;
-       backpatch(p, gen_retblk(0));
-       root = p->head;
 
        /*
         * Insert before the statements of the first (root) block any
@@ -518,13 +506,30 @@ finish_parse(p)
         * statements of all blocks that use those lengths and that
         * have no predecessors that use them, so that we only compute
         * the lengths if we need them.  There might be even better
-        * approaches than that.  However, as we're currently only
-        * handling variable-length radiotap headers, and as all
-        * filtering expressions other than raw link[M:N] tests
-        * require the length of that header, doing more for that
-        * header length isn't really worth the effort.
+        * approaches than that.
+        *
+        * However, those strategies would be more complicated, and
+        * as we don't generate code to compute a length if the
+        * program has no tests that use the length, and as most
+        * tests will probably use those lengths, we would just
+        * postpone computing the lengths so that it's not done
+        * for tests that fail early, and it's not clear that's
+        * worth the effort.
+        */
+       insert_compute_vloffsets(p->head);
+       
+       /*
+        * For DLT_PPI captures, generate a check of the per-packet
+        * DLT value to make sure it's DLT_IEEE802_11.
         */
-       insert_load_llprefixlen(root);
+       ppi_dlt_check = gen_ppi_dlt_check();
+       if (ppi_dlt_check != NULL)
+               gen_and(ppi_dlt_check, p);
+
+       backpatch(p, gen_retblk(snaplen));
+       p->sense = !p->sense;
+       backpatch(p, gen_retblk(0));
+       root = p->head;
 }
 
 void
@@ -2379,15 +2384,16 @@ gen_load_802_11_header_len(struct slist *s, struct slist *snext)
 }
 
 static void
-insert_load_llprefixlen(b)
+insert_compute_vloffsets(b)
        struct block *b;
 {
        struct slist *s;
 
        /*
-        * Generate code to load the length of any variable-length
-        * header preceding the link-layer header into the register
-        * assigned to that length, if any.
+        * For link-layer types that have a variable-length header
+        * preceding the link-layer header, generate code to load
+        * the offset of the link-layer header into the register
+        * assigned to that offset, if any.
         */
        switch (linktype) {
 
@@ -2405,9 +2411,9 @@ insert_load_llprefixlen(b)
        }
 
        /*
-        * Now generate code to load the length of any variable-length
-        * header preceding the link-layer header into the register
-        * assigned to that length, if any.
+        * For link-layer types that have a variable-length link-layer
+        * header, generate code to load the offset of the MAC-layer
+        * payload into the register assigned to that offset, if any.
         */
        switch (linktype) {
 
@@ -2421,7 +2427,7 @@ insert_load_llprefixlen(b)
        }
 
        /*
-        * If we have any length loading code, append all the
+        * If we have any offset-loading code, append all the
         * existing statements in the block to those statements,
         * and make the resulting list the list of statements
         * for the block.