Include fixed offset when computing variable MAC headers.

[libpcap] / gencode.c

diff --git a/gencode.c b/gencode.c
index 8eb8cd216da9963833adb28deab1d3b49dade0aa..6383a7a785572ebac76a8bc92499c481d049012d 100644 (file)
--- a/gencode.c
+++ b/gencode.c
@@ -806,6 +806,11 @@ static u_int off_mac;
  * for example, any 802.2 LLC header, so it's the MAC-layer
  * portion of that header), plus any prefix preceding the
  * link-layer header.
+ *
+ * In the event of a variable length MAC header, this is typically
+ * 0. However, it can be used as a fixed component added to the
+ * variable piece, such as in the case of a VLAN increasing the size
+ * of the header.
  */
 static u_int off_macpl;
 
@@ -1554,7 +1559,7 @@ gen_load_macplrel(offset, size)
                 * as an offset.
                 */
                s2 = new_stmt(BPF_LD|BPF_IND|size);
-               s2->s.k = offset;
+               s2->s.k = off_macpl + offset;
                sappend(s, s2);
        } else {
                /*