From: Guy Harris <guy@alum.mit.edu>
Date: Sun, 19 Aug 2012 02:19:53 +0000 (-0700)
Subject: Handle VLAN tags in cooked mode.
X-Git-Url: https://git.tcpdump.org/libpcap/commitdiff_plain/3fcdfec27fbfb7bcff89e8671644130f50993bf6

Handle VLAN tags in cooked mode.

Use Jakub Zawadzki's changes for that, but put the VLAN tag offset into
the pcap structure and calculate it at activation time.
---

diff --git a/pcap-int.h b/pcap-int.h
index a34ee8e7..6616f176 100644
--- a/pcap-int.h
+++ b/pcap-int.h
@@ -144,7 +144,7 @@ struct pcap_md {
 	char	*mondevice;	/* mac80211 monitor device we created */
 	u_char	*mmapbuf;	/* memory-mapped region pointer */
 	size_t	mmapbuflen;	/* size of region */
-	int	add_vlan_tags;	/* 1 if we should insert VLAN tags */
+	int	vlan_offset;	/* offset at which to insert vlan tags; if -1, don't insert */
 	u_int	tp_version;	/* version of tpacket_hdr for mmaped ring */
 	u_int	tp_hdrlen;	/* hdrlen of tpacket_hdr for mmaped ring */
 	u_char	*oneshot_buffer; /* buffer for copy of packet */
diff --git a/pcap-linux.c b/pcap-linux.c
index caf1a256..70ad282d 100644
--- a/pcap-linux.c
+++ b/pcap-linux.c
@@ -1618,7 +1618,7 @@ pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
 	}
 
 #if defined(HAVE_PACKET_AUXDATA) && defined(HAVE_LINUX_TPACKET_AUXDATA_TP_VLAN_TCI)
-	if (handle->md.add_vlan_tags) {
+	if (handle->md.vlan_offset != -1) {
 		for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 			struct tpacket_auxdata *aux;
 			unsigned int len;
@@ -1634,13 +1634,13 @@ pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
 				continue;
 
 			len = packet_len > iov.iov_len ? iov.iov_len : packet_len;
-			if (len < 2 * ETH_ALEN)
+			if (len < (unsigned int) handle->md.vlan_offset)
 				break;
 
 			bp -= VLAN_TAG_LEN;
-			memmove(bp, bp + VLAN_TAG_LEN, 2 * ETH_ALEN);
+			memmove(bp, bp + VLAN_TAG_LEN, handle->md.vlan_offset);
 
-			tag = (struct vlan_tag *)(bp + 2 * ETH_ALEN);
+			tag = (struct vlan_tag *)(bp + handle->md.vlan_offset);
 			tag->vlan_tpid = htons(ETH_P_8021Q);
 			tag->vlan_tci = htons(aux->tp_vlan_tci);
 
@@ -3184,17 +3184,22 @@ activate_new(pcap_t *handle)
 	handle->bufsize = handle->snapshot;
 
 	/*
-	 * Only enable the insertion of VLAN tags if the link-layer
-	 * header type is Ethernet.  If it should be supported on
-	 * any other link-layer type, the code that inserts them
-	 * must be modified to insert them in the proper place, which
-	 * differs from link-layer header type to link-layer header
-	 * type.
+	 * Set the offset at which to insert VLAN tags.
 	 */
-	if (handle->linktype == DLT_EN10MB)
-		handle->md.add_vlan_tags = 1;
-	else
-		handle->md.add_vlan_tags = 0;
+	switch (handle->linktype) {
+
+	case DLT_EN10MB:
+		handle->md.vlan_offset = 2 * ETH_ALEN;
+		break;
+
+	case DLT_LINUX_SLL:
+		handle->md.vlan_offset = 14;
+		break;
+
+	default:
+		handle->md.vlan_offset = -1; /* unknown */
+		break;
+	}
 
 	/* Save the socket FD in the pcap structure */
 	handle->fd = sock_fd;
@@ -3283,14 +3288,6 @@ activate_mmap(pcap_t *handle, int *status)
 	handle->getnonblock_op = pcap_getnonblock_mmap;
 	handle->oneshot_callback = pcap_oneshot_mmap;
 	handle->selectable_fd = handle->fd;
-
-	/*
-	 * We only support inserting VLAN tags for tpacket V2;
-	 * if we're using v1, disable it.
-	 */
-	if (handle->md.tp_version == TPACKET_V1)
-		handle->md.add_vlan_tags = 0;
-
 	return 1;
 }
 #else /* HAVE_PACKET_RING */
@@ -4043,14 +4040,15 @@ pcap_read_linux_mmap(pcap_t *handle, int max_packets, pcap_handler callback,
 		}
 
 #ifdef HAVE_TPACKET2
-		if (handle->md.add_vlan_tags && h.h2->tp_vlan_tci &&
-		    tp_snaplen >= 2 * ETH_ALEN) {
+		if (handle->md.tp_version == TPACKET_V2 && h.h2->tp_vlan_tci &&
+		    handle->md.vlan_offset != -1 &&
+		    tp_snaplen >= (unsigned int) handle->md.vlan_offset) {
 			struct vlan_tag *tag;
 
 			bp -= VLAN_TAG_LEN;
-			memmove(bp, bp + VLAN_TAG_LEN, 2 * ETH_ALEN);
+			memmove(bp, bp + VLAN_TAG_LEN, handle->md.vlan_offset);
 
-			tag = (struct vlan_tag *)(bp + 2 * ETH_ALEN);
+			tag = (struct vlan_tag *)(bp + handle->md.vlan_offset);
 			tag->vlan_tpid = htons(ETH_P_8021Q);
 			tag->vlan_tci = htons(h.h2->tp_vlan_tci);
 
@@ -5237,9 +5235,10 @@ activate_old(pcap_t *handle)
 	handle->offset	 = 0;
 
 	/*
-	 * No support for getting VLAN tags to insert.
+	 * SOCK_PACKET sockets don't supply information from
+	 * stripped VLAN tags.
 	 */
-	handle->md.add_vlan_tags = 0;
+	handle->md.vlan_offset = -1; /* unknown */
 
 	return 1;
 }