[PATCH] libceph: accept addrvecs with multiple entries of the same type

[Kefu Chai]

ceph_decode_entity_addrvec() rejects any addrvec containing more than
one entry that matches the requested msgr type (LEGACY or MSGR2),
logging "another match of type N in addrvec" and returning -EINVAL.
This breaks legitimate deployments where a daemon advertises multiple
addresses of the same type, most notably dual-stack (IPv4 + IPv6)
clusters and multi-subnet deployments where tooling picks one address
per listed public_network.

The monmap decoder fails, the client enters a reconnect loop:

  libceph: mon0 (1)10.10.10.15:6789 session established
  libceph: another match of type 1 in addrvec
  libceph: problem decoding monmap, -22

Match the userspace messenger, which since Nautilus picks the first
entry of the requested type and silently tolerates subsequent entries.

Link: https://tracker.ceph.com/issues/49581
Link: https://tracker.ceph.com/issues/64068
Link: https://bugzilla.proxmox.com/show_bug.cgi?id=7518
Signed-off-by: Kefu Chai <k.chai@xxxxxxxxxxx>
---

Tested by reproducing the Proxmox BZ 7518 scenario against a vstart
cluster whose mon addrvec was edited to contain two v1 + two v2 entries:

    ceph mon set-addrs a \\
        '[v2:$ip1:$p2/0,v1:$ip1:$p1/0,v2:$ip2:$p2/0,v1:$ip2:$p1/0]'

A Debian VM booted with the patched kernel via 'qemu -kernel' then
ran 'mount -t ceph ...:$p1:/ /mnt -o name=admin'.  Pre-patch kernels
fail at monmap decode with "another match of type 1 in addrvec"
(-EINVAL).  Post-patch, decode succeeds and the mount proceeds to
the auth / MDS-discovery stages.

Also verified the decoder logic on the monmap.bin attached to BZ 7518
using a userspace port of ceph_decode_entity_addrvec(): the pre-patch
form returns -EINVAL on both msgr1 and msgr2 lookups; the post-patch
form returns 0 and picks the first matching entry.

 net/ceph/decode.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/net/ceph/decode.c b/net/ceph/decode.c
index bc109a1a4616..b17bc082b4fc 100644
--- a/net/ceph/decode.c
+++ b/net/ceph/decode.c
@@ -88,7 +88,8 @@ EXPORT_SYMBOL(ceph_decode_entity_addr);
 
 /*
  * Return addr of desired type (MSGR2 or LEGACY) or error.
- * Make sure there is only one match.
+ * If multiple entries of the desired type are present, use the
+ * first one.
  *
  * Assume encoding with MSG_ADDR2.
  */
@@ -120,13 +121,7 @@ int ceph_decode_entity_addrvec(void **p, void *end, bool msgr2,
 			return ret;
 
 		dout("%s i %d addr %s\n", __func__, i, ceph_pr_addr(&tmp_addr));
-		if (tmp_addr.type == my_type) {
-			if (found) {
-				pr_err("another match of type %d in addrvec\n",
-				       le32_to_cpu(my_type));
-				return -EINVAL;
-			}
-
+		if (tmp_addr.type == my_type && !found) {
 			memcpy(addr, &tmp_addr, sizeof(*addr));
 			found = true;
 		}
-- 
2.47.3