ofproto-xlate: Fix crash when forwarding packet between legacy_l3 tunnels.

A packet received from a tunnel port with legacy_l3 packet-type (e.g.
lisp, L3 gre, gtpu) is conceptually wrapped in a dummy Ethernet header
for processing in an OF pipeline that is not packet-type-aware. Before
transmission of the packet to another legacy_l3 tunnel port, the dummy
Ethernet header is stripped again.

In ofproto-xlate, wrapping in the dummy Ethernet header is done by
simply changing the packet_type to PT_ETH. The generation of the
push_eth datapath action is deferred until the packet's flow changes
need to be committed, for example at output to a normal port. The
deferred Ethernet encapsulation is marked in the pending_encap flag.

This patch fixes a bug in the translation of the output action to a
legacy_l3 tunnel port, where the packet_type of the flow is reverted
from PT_ETH to PT_IPV4 or PT_IPV6 (depending on the dl_type) to remove
its Ethernet header without clearing the pending_encap flag if it was
set. At the subsequent commit of the flow changes, the unexpected
combination of pending_encap == true with an PT_IPV4 or PT_IPV6
packet_type hit the OVS_NOT_REACHED() abortion clause.

The pending_encap is now cleared in this situation.

Reported-by: Dincer Beken <dbeken@blackned.de>
Signed-off-by: Jan Scheurich <jan.scheurich@ericsson.com>
Co-authored-by: Dincer Beken <dbeken@blackned.de>
Signed-off-by: Dincer Beken <dbeken@blackned.de>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index 5a770f171..d085c5ba5 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -4195,6 +4195,10 @@ compose_output_action__(struct xlate_ctx *ctx, ofp_port_t ofp_port,
         if (xport->pt_mode == NETDEV_PT_LEGACY_L3) {
             flow->packet_type = PACKET_TYPE_BE(OFPHTN_ETHERTYPE,
                                                ntohs(flow->dl_type));
+            if (ctx->pending_encap) {
+                /* The Ethernet header was not actually added yet. */
+                ctx->pending_encap = false;
+            }
         }
     }