Handle the three types of link layers:

	those that always use 802.2;

	those that never use 802.2;

	Ethernet (where 802.2 is used for 802.3 and is not used for
	Ethernet II);

correctly.  This requires having two variables for the offset of the
network layer header, one for use with protocols that would not run atop
802.2 on Ethernet and would run atop 802.2+SNAP on link layers that
always use 802.2, and one for use with protosol that would run atop
raw 802.2 (no SNAP) on Ethernet and on link layers that always use
802.2.

Fix the network layer offset for 802.11, and the link-layer offset for
RFC 1483 ATM (there's no link layer, there's just 802.2 LLC).

diff --git a/gencode.c b/gencode.c
index 1a5361f61ec2bd504c875f972efef19f125eb668..d44ec9b546547b5a54a8bced15ae63c95431b0fd 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 1.163 2002-04-07 00:04:37 guy Exp $ (LBL)";
+    "@(#) $Header: /tcpdump/master/libpcap/gencode.c,v 1.164 2002-04-11 07:38:32 guy Exp $ (LBL)";
 #endif
 
 #ifdef HAVE_CONFIG_H
@@ -78,7 +78,7 @@ static jmp_buf top_ctx;
 static pcap_t *bpf_pcap;
 
 /* Hack for updating VLAN offsets. */
-static u_int   orig_linktype = -1, orig_nl = -1;
+static u_int   orig_linktype = -1, orig_nl = -1, orig_nl_nosnap = -1;
 
 /* XXX */
 #ifdef PCAP_FDDIPAD
@@ -540,11 +540,55 @@ gen_bcmp(offset, size, v)
 
 /*
  * Various code constructs need to know the layout of the data link
- * layer.  These variables give the necessary offsets.  off_linktype
- * is set to -1 for no encapsulation, in which case, IP is assumed.
+ * layer.  These variables give the necessary offsets.
+ */
+
+/*
+ * "off_linktype" is the offset to information in the link-layer header
+ * giving the packet type.
+ *
+ * For Ethernet, it's the offset of the Ethernet type field.
+ *
+ * For link-layer types that always use 802.2 headers, it's the
+ * offset of the LLC header.
+ *
+ * For PPP, it's the offset of the PPP type field.
+ *
+ * For Cisco HDLC, it's the offset of the CHDLC type field.
+ *
+ * For BSD loopback, it's the offset of the AF_ value.
+ *
+ * For Linux cooked sockets, it's the offset of the type field.
+ *
+ * It's set to -1 for no encapsulation, in which case, IP is assumed.
  */
 static u_int off_linktype;
+
+/*
+ * These are offsets to the beginning of the network-layer header.
+ *
+ * If the link layer never uses 802.2 LLC:
+ *
+ *     "off_nl" and "off_nl_nosnap" are the same.
+ *
+ * If the link layer always uses 802.2 LLC:
+ *
+ *     "off_nl" is the offset if there's a SNAP header following
+ *     the 802.2 header;
+ *
+ *     "off_nl_nosnap" is the offset if there's no SNAP header.
+ *
+ * If the link layer is Ethernet:
+ *
+ *     "off_nl" is the offset if the packet is an Ethernet II packet
+ *     (we assume no 802.3+802.2+SNAP);
+ *
+ *     "off_nl_nosnap" is the offset if the packet is an 802.3 packet
+ *     with an 802.2 header following it.
+ */
 static u_int off_nl;
+static u_int off_nl_nosnap;
+
 static int linktype;
 
 static void
@@ -555,17 +599,20 @@ init_linktype(type)
 
        orig_linktype = -1;
        orig_nl = -1;
+       orig_nl_nosnap = -1;
 
        switch (type) {
 
        case DLT_ARCNET:
                off_linktype = 2;
                off_nl = 6;     /* XXX in reality, variable! */
+               off_nl_nosnap = 6;      /* no 802.2 LLC */
                return;
 
        case DLT_EN10MB:
                off_linktype = 12;
-               off_nl = 14;
+               off_nl = 14;            /* Ethernet II */
+               off_nl_nosnap = 17;     /* 802.3+802.2 */
                return;
 
        case DLT_SLIP:
@@ -575,6 +622,7 @@ init_linktype(type)
                 */
                off_linktype = -1;
                off_nl = 16;
+               off_nl_nosnap = 16;     /* no 802.2 LLC */
                return;
 
        case DLT_SLIP_BSDOS:
@@ -582,12 +630,14 @@ init_linktype(type)
                off_linktype = -1;
                /* XXX end */
                off_nl = 24;
+               off_nl_nosnap = 24;     /* no 802.2 LLC */
                return;
 
        case DLT_NULL:
        case DLT_LOOP:
                off_linktype = 0;
                off_nl = 4;
+               off_nl_nosnap = 4;      /* no 802.2 LLC */
                return;
 
        case DLT_PPP:
@@ -595,6 +645,7 @@ init_linktype(type)
        case DLT_PPP_SERIAL:            /* NetBSD sync/async serial PPP */
                off_linktype = 2;
                off_nl = 4;
+               off_nl_nosnap = 4;      /* no 802.2 LLC */
                return;
 
        case DLT_PPP_ETHER:
@@ -604,11 +655,13 @@ init_linktype(type)
                 */
                off_linktype = 6;
                off_nl = 8;
+               off_nl_nosnap = 8;      /* no 802.2 LLC */
                return;
 
        case DLT_PPP_BSDOS:
                off_linktype = 5;
                off_nl = 24;
+               off_nl_nosnap = 24;     /* no 802.2 LLC */
                return;
 
        case DLT_FDDI:
@@ -624,9 +677,11 @@ init_linktype(type)
 #ifdef PCAP_FDDIPAD
                off_linktype += pcap_fddipad;
 #endif
-               off_nl = 21;
+               off_nl = 21;            /* FDDI+802.2+SNAP */
+               off_nl_nosnap = 16;     /* FDDI+802.2 */
 #ifdef PCAP_FDDIPAD
                off_nl += pcap_fddipad;
+               off_nl_nosnap += pcap_fddipad;
 #endif
                return;
 
@@ -655,7 +710,8 @@ init_linktype(type)
                 * 8 - figure out which byte that is).
                 */
                off_linktype = 14;
-               off_nl = 22;
+               off_nl = 22;            /* Token Ring+802.2+SNAP */
+               off_nl_nosnap = 17;     /* Token Ring+802.2 */
                return;
 
        case DLT_IEEE802_11:
@@ -672,7 +728,8 @@ init_linktype(type)
                 * data frames in networks with no bridges.
                 */
                off_linktype = 24;
-               off_nl = 30;
+               off_nl = 32;            /* 802.11+802.2+SNAP */
+               off_nl_nosnap = 27;     /* 802.22+802.2 */
                return;
 
        case DLT_PRISM_HEADER:
@@ -687,31 +744,31 @@ init_linktype(type)
                 * the Prism header is fixed-length.
                 */
                off_linktype = 144+24;
-               off_nl = 144+30;
+               off_nl = 144+32;        /* Prism+802.11+802.2+SNAP */
+               off_nl_nosnap = 144+27; /* Prism+802.11+802.2 */
                return;
 
        case DLT_ATM_RFC1483:
+       case DLT_ATM_CLIP:      /* Linux ATM defines this */
                /*
                 * assume routed, non-ISO PDUs
                 * (i.e., LLC = 0xAA-AA-03, OUT = 0x00-00-00)
                 */
-               off_linktype = 6;
-               off_nl = 8;
+               off_linktype = 0;
+               off_nl = 8;             /* 802.2+SNAP */
+               off_nl_nosnap = 3;      /* 802.2 */
                return;
 
        case DLT_RAW:
                off_linktype = -1;
                off_nl = 0;
-               return;
-
-       case DLT_ATM_CLIP:      /* Linux ATM defines this */
-               off_linktype = 6;
-               off_nl = 8;
+               off_nl_nosnap = 0;      /* no 802.2 LLC */
                return;
 
        case DLT_LINUX_SLL:     /* fake header for Linux cooked socket */
                off_linktype = 14;
                off_nl = 16;
+               off_nl_nosnap = 16;     /* no 802.2 LLC */
                return;
 
        case DLT_LTALK:
@@ -722,6 +779,7 @@ init_linktype(type)
                 */
                off_linktype = -1;
                off_nl = 0;
+               off_nl_nosnap = 0;      /* no 802.2 LLC */
                return;
        }
        bpf_error("unknown data link type %d", linktype);
@@ -2789,7 +2847,7 @@ gen_proto(v, proto, dir)
 
        case Q_ISO:
                b0 = gen_linktype(LLCSAP_ISONS);
-               b1 = gen_cmp(off_nl + 3, BPF_B, (long)v);
+               b1 = gen_cmp(off_nl_nosnap, BPF_B, (long)v);
                gen_and(b0, b1);
                return b1;
 
@@ -3905,11 +3963,13 @@ gen_vlan(vlan_num)
        if (orig_nl == (u_int)-1) {
                orig_linktype = off_linktype;   /* save original values */
                orig_nl = off_nl;
+               orig_nl_nosnap = off_nl_nosnap;
 
                switch (linktype) {
 
                case DLT_EN10MB:
                        off_linktype = 16;
+                       off_nl_nosnap = 18;
                        off_nl = 18;
                        break;