[ovs-dev] [PATCH] bfd: Support overlay BFD

Yifeng Sun pkusunyifeng at gmail.com
Wed Jun 24 20:58:23 UTC 2020


Current OVS intercepts and processes all BFD packets, thus VM-2-VM
BFD packets get lost and the recipient VM never sees them.

This patch fixes it by only intercepting and processing BFD packets
destined to a configured BFD instance, and other BFD packets are made
available to the OVS flow table for forwarding.

This patch keeps BFD's backward compatibility.

Signed-off-by: Yifeng Sun <pkusunyifeng at gmail.com>
---
 lib/bfd.c            | 16 +++++++++++++---
 vswitchd/vswitch.xml |  7 +++++++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/lib/bfd.c b/lib/bfd.c
index cc8c6857afa4..3c965699ace3 100644
--- a/lib/bfd.c
+++ b/lib/bfd.c
@@ -149,6 +149,9 @@ BUILD_ASSERT_DECL(BFD_PACKET_LEN == sizeof(struct msg));
 #define FLAGS_MASK 0x3f
 #define DEFAULT_MULT 3
 
+#define BFD_DEFAULT_SRC_IP 0xA9FE0101 /* 169.254.1.1 */
+#define BFD_DEFAULT_DST_IP 0xA9FE0100 /* 169.254.1.0 */
+
 struct bfd {
     struct hmap_node node;        /* In 'all_bfds'. */
     uint32_t disc;                /* bfd.LocalDiscr. Key in 'all_bfds' hmap. */
@@ -457,9 +460,9 @@ bfd_configure(struct bfd *bfd, const char *name, const struct smap *cfg,
                          &bfd->rmt_eth_dst);
 
     bfd_lookup_ip(smap_get_def(cfg, "bfd_src_ip", ""),
-                  htonl(0xA9FE0101) /* 169.254.1.1 */, &bfd->ip_src);
+                  htonl(BFD_DEFAULT_SRC_IP), &bfd->ip_src);
     bfd_lookup_ip(smap_get_def(cfg, "bfd_dst_ip", ""),
-                  htonl(0xA9FE0100) /* 169.254.1.0 */, &bfd->ip_dst);
+                  htonl(BFD_DEFAULT_DST_IP), &bfd->ip_dst);
 
     forwarding_if_rx = smap_get_bool(cfg, "forwarding_if_rx", false);
     if (bfd->forwarding_if_rx != forwarding_if_rx) {
@@ -674,7 +677,14 @@ bfd_should_process_flow(const struct bfd *bfd_, const struct flow *flow,
         memset(&wc->masks.nw_proto, 0xff, sizeof wc->masks.nw_proto);
         if (flow->nw_proto == IPPROTO_UDP
             && !(flow->nw_frag & FLOW_NW_FRAG_LATER)
-            && tp_dst_equals(flow, BFD_DEST_PORT, wc)) {
+            && tp_dst_equals(flow, BFD_DEST_PORT, wc)
+            && (bfd->ip_src == htonl(BFD_DEFAULT_SRC_IP)
+                || bfd->ip_src == flow->nw_dst)) {
+
+            if (bfd->ip_src == flow->nw_dst) {
+                memset(&wc->masks.nw_dst, 0xffffffff, sizeof wc->masks.nw_dst);
+            }
+
             bool check_tnl_key;
 
             atomic_read_relaxed(&bfd->check_tnl_key, &check_tnl_key);
diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
index b6acb34ca1b8..e1f895134ff2 100644
--- a/vswitchd/vswitch.xml
+++ b/vswitchd/vswitch.xml
@@ -3662,6 +3662,13 @@ ovs-vsctl add-port br0 p0 -- set Interface p0 type=patch options:peer=p1 \
         optional Authentication or ``Echo Mode'' features.
       </p>
 
+      <p>
+        OVS 2.13 and earlier intercepted and processed all BFD packets.
+        OVS 2.14 and later only intercept and process BFD packets destined
+        to a configured BFD instance, and other BFD packets are made available
+        to the OVS flow table for forwarding.
+      </p>
+
       <group title="BFD Configuration">
         <p>
           A controller sets up key-value pairs in the <ref column="bfd"/>
-- 
2.7.4



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