From: Benoît Ganne <bganne@cisco.com>
Date: Tue, 17 Sep 2019 15:30:35 +0000 (+0200)
Subject: interface: fix pcap drop trace in case of vlan
X-Git-Tag: v19.08.2~346
X-Git-Url: https://gerrit.fd.io/r/gitweb?a=commitdiff_plain;h=2cf5b1a1ec8d959f1355974822deba35d6bfb04b;p=vpp.git

interface: fix pcap drop trace in case of vlan

Type: fix

Change-Id: If3c4e5c376b51a26143d8922dcacfbda534163bd
Signed-off-by: Benoît Ganne <bganne@cisco.com>
(cherry picked from commit 4e323cbdbd57fcd77db68e295f639288441ef3e3)
---

diff --git a/src/vnet/interface_output.c b/src/vnet/interface_output.c
index 250d0dbe251..5d3d53e5ad8 100644
--- a/src/vnet/interface_output.c
+++ b/src/vnet/interface_output.c
@@ -1207,8 +1207,19 @@ pcap_drop_trace (vlib_main_t * vm,
 
 	  /*
 	   * Typically, we'll need to rewind the buffer
+	   * if l2_hdr_offset is valid, make sure to rewind to the start of
+	   * the L2 header. This may not be the buffer start in case we pop-ed
+	   * vlan tags.
+	   * Otherwise, rewind to buffer start and hope for the best.
 	   */
-	  if (b0->current_data > 0)
+	  if (b0->flags & VNET_BUFFER_F_L2_HDR_OFFSET_VALID)
+	    {
+	      if (b0->current_data > vnet_buffer (b0)->l2_hdr_offset)
+		vlib_buffer_advance (b0,
+				     vnet_buffer (b0)->l2_hdr_offset -
+				     b0->current_data);
+	    }
+	  else if (b0->current_data > 0)
 	    vlib_buffer_advance (b0, (word) - b0->current_data);
 
 	  pcap_add_buffer (&im->pcap_main, vm, bi0, 512);