stn-plugin: do not assume all punted packets start with L3 header.

Some punt scenarios (notably, involving DNS traffic)
do not have the current_data set to the L3 header -
as a result, chaos ensues. To tackle this, approach
the parsing from the other side, and look at
the hopefully remaining ethernet header
to see whether the packet is IPv4 or IPv6.

Verified the STN'ed TCP traffic continues to work,
and that the STN'ed DNS traffic starts to work as well.

Change-Id: I0aa2ad1df2fb23dd4e54a564714103b19114d636
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

diff --git a/src/plugins/stn/stn.c b/src/plugins/stn/stn.c
index a9e6a98..b05883b 100644 (file)
--- a/src/plugins/stn/stn.c
+++ b/src/plugins/stn/stn.c
@@ -109,8 +109,20 @@ stn_punt_fn (vlib_main_t * vm,
 
          p0 = vlib_get_buffer (vm, pi0);
 
+/*
+ * We are not guaranteed any particular layer here.
+ * So we need to reparse from the beginning of the packet.
+ * which may not start from zero with some DPDK drivers.
+
          ip4_header_t *ip = vlib_buffer_get_current(p0);
          if ((ip->ip_version_and_header_length & 0xf0) == 0x40)
+*
+*/
+         int ethernet_header_offset = 0; /* to be filled by DPDK */
+         ethernet_header_t *eth = (ethernet_header_t *)(p0->data + ethernet_header_offset);
+         /* ensure the block current data starts at L3 boundary now for the subsequent nodes */
+         vlib_buffer_advance(p0, ethernet_header_offset + sizeof(ethernet_header_t) - p0->current_data);
+          if (clib_net_to_host_u16(eth->type) == ETHERNET_TYPE_IP4)
            next0 = stn->punt_to_stn_ip4_next_index;
          else
            next0 = stn->punt_to_stn_ip6_next_index;