bfd: Allow setting OAM bit when encapsulated in tunnel.

Some tunnel protocols, such as Geneve, have a bit in the tunnel
header to indicate that it is an OAM packet. This means that the
packet should be processed as a tunnel control frame and not be
passed onto connected links.

When BFD is used inside of a tunnel it is often used in this control
capacity, so this adds an option to enable marking the outer header
when the output port is a tunnel that supports the OAM concept. It is
also possible to use tunnels as point-to-point links that are simply
carrying BFD as payload, so this is not always turned on.

Conceptually, this may also apply to other types of packets locally
generated by the switch, most obviously CFM. However, BFD seems to
be most commonly used for this type of tunnel monitoring application
so this only adds the option to BFD for the time being to avoid
unnecessarily adding configuration knobs that might never get used.

Signed-off-by: Jesse Gross <jesse@kernel.org>
Acked-by: Pravin B Shelar <pshelar@ovn.org>

2 files changed, 7 insertions, 2 deletions

diff --git a/lib/bfd.c b/lib/bfd.c
index b40c02247..9616c9003 100644
--- a/lib/bfd.c
+++ b/lib/bfd.c
@@ -168,6 +168,8 @@ struct bfd {
     enum flags flags;             /* Flags sent on messages. */
     enum flags rmt_flags;         /* Flags last received. */
 
+    bool oam;                     /* Set tunnel OAM flag if applicable. */
+
     uint32_t rmt_disc;            /* bfd.RemoteDiscr. */
 
     struct eth_addr local_eth_src; /* Local eth src address. */
@@ -390,6 +392,8 @@ bfd_configure(struct bfd *bfd, const char *name, const struct smap *cfg,
         bfd_status_changed(bfd);
     }
 
+    bfd->oam = smap_get_bool(cfg, "oam", false);
+
     atomic_store_relaxed(&bfd->check_tnl_key,
                          smap_get_bool(cfg, "check_tnl_key", false));
     min_tx = smap_get_int(cfg, "min_tx", 100);
@@ -586,7 +590,7 @@ bfd_should_send_packet(const struct bfd *bfd) OVS_EXCLUDED(mutex)
 
 void
 bfd_put_packet(struct bfd *bfd, struct dp_packet *p,
-               const struct eth_addr eth_src) OVS_EXCLUDED(mutex)
+               const struct eth_addr eth_src, bool *oam) OVS_EXCLUDED(mutex)
 {
     long long int min_tx, min_rx;
     struct udp_header *udp;
@@ -654,6 +658,7 @@ bfd_put_packet(struct bfd *bfd, struct dp_packet *p,
     msg->min_rx = htonl(min_rx * 1000);
 
     bfd->flags &= ~FLAG_FINAL;
+    *oam = bfd->oam;
 
     log_msg(VLL_DBG, msg, "Sending BFD Message", bfd);
 
diff --git a/lib/bfd.h b/lib/bfd.h
index 6a1d547cc..9d32327fb 100644
--- a/lib/bfd.h
+++ b/lib/bfd.h
@@ -36,7 +36,7 @@ void bfd_run(struct bfd *);
 
 bool bfd_should_send_packet(const struct bfd *);
 void bfd_put_packet(struct bfd *bfd, struct dp_packet *packet,
-                    const struct eth_addr eth_src);
+                    const struct eth_addr eth_src, bool *oam);
 
 bool bfd_should_process_flow(const struct bfd *, const struct flow *,
                              struct flow_wildcards *);