[PATCH net-next v6 0/2] net/rds: scope-aware sendmsg connection cache

[Allison Henderson <achender@kernel.org>]

Hi all,

This is v6 of the sendmsg connection-cache scope fix (v1 at [1], v2 at
[2], v3 at [3], v4 at [4], v5 at [5]), against net-next as Jakub
suggested: neither issue has been observed in the field, and both were
found by inspection while reworking this cache for the
connection-lifetime series.

  Patch 1 compares c_dev_if with the request's scope in the cache-hit
  test, so the cache uses the same key as rds_conn_lookup().

  Patch 2 gives the connected peer's link-local scope its own field.
  rds_connect() used to store it in rs_bound_scope_id, the scope of
  the socket's own bound address, which a later bind() to a
  non-link-local address resets to 0 and which a later connect()
  pollutes for a globally bound socket.  A send without a destination
  and getpeername() take the connected peer's scope from that field;
  recvmsg() reports a link-local sender with the interface recorded
  on its connection.

Changes since v5 [5]:
 - Swapped the two patches.  The scope-field patch lets a globally
   bound socket connect() to the same link-local peer through a second
   interface, and without the cache check in place first the next
   send() would reuse the first interface's connection, so the series
   is now bisectable (review of v5).
 - recvmsg() comment and changelog no longer describe c_dev_if as the
   arrival interface: that holds for TCP, while the IB passive side
   resolves it from the local address (review of v5).
 - No code change beyond the comment.

Changes since v4 [4]:
 - recvmsg() takes a link-local sender's scope from the connection the
   message arrived on (c_dev_if) and reports 0 for any other sender,
   instead of the socket's connected or bound scope - a connected
   socket receives from any peer, so a per-socket scope was wrong for
   every sender but the connected one and could send a reply out the
   wrong link (review of v4).  getpeername() and recvmsg() now agree
   for the connected peer.
 - Retargeted at net-next.

Changes since v3 [3]:
 - A destination-less send falls back to the bound scope for a
   non-link-local peer, so send() and sendto() to the connected peer
   compute the same scope; getpeername() and recvmsg() report the
   connected peer's scope instead of the bound scope.

[1] https://lore.kernel.org/netdev/20260921215046.174745-1-achender@kernel.org/
[2] https://lore.kernel.org/netdev/20260927062312.169097-1-achender@kernel.org/
[3] https://lore.kernel.org/netdev/20261003163526.250805-1-achender@kernel.org/
[4] https://lore.kernel.org/netdev/20261008031426.1142344-1-achender@kernel.org/
[5] https://lore.kernel.org/netdev/20261017032358.2563121-1-achender@kernel.org/

Thank you,
Allison

Allison Henderson (2):
  net/rds: include the scope id in the sendmsg connection cache check
  net/rds: keep the connected peer's scope id apart from the bound one

 net/rds/af_rds.c | 15 +++++++++------
 net/rds/bind.c   |  4 ++--
 net/rds/rds.h    |  2 ++
 net/rds/recv.c   | 11 ++++++++++-
 net/rds/send.c   |  9 +++++++--
 5 files changed, 30 insertions(+), 11 deletions(-)

-- 
2.50.1