On 3/19/25 1:02 PM, Nikhil Jha via B4 Relay wrote: > When the client retransmits an operation (for example, because the > server is slow to respond), a new GSS sequence number is associated with > the XID. In the current kernel code the original sequence number is > discarded. Subsequently, if a response to the original request is > received there will be a GSS sequence number mismatch. A mismatch will > trigger another retransmit, possibly repeating the cycle, and after some > number of failed retries EACCES is returned. > > RFC2203, section 5.3.3.1 suggests a possible solution... “cache the > RPCSEC_GSS sequence number of each request it sends” and "compute the > checksum of each sequence number in the cache to try to match the > checksum in the reply's verifier." This is what FreeBSD’s implementation > does (rpc_gss_validate in sys/rpc/rpcsec_gss/rpcsec_gss.c). > > However, even with this cache, retransmits directly caused by a seqno > mismatch can still cause a bad message interleaving that results in this > bug. The RFC already suggests ignoring incorrect seqnos on the server > side, and this seems symmetric, so this patchset also applies that > behavior to the client. > > These two patches are *not* dependent on each other. I tested them by > delaying packets with a Python script hooked up to NFQUEUE. If it would > be helpful I can send this script along as well. > > Signed-off-by: Nikhil Jha <[email protected]> > --- > Changes since v1: > * Maintain the invariant that the first seqno is always first in > rq_seqnos, so that it doesn't need to be stored twice. > * Minor formatting, and resending with proper mailing-list headers so the > patches are easier to work with. > > --- > Nikhil Jha (2): > sunrpc: implement rfc2203 rpcsec_gss seqnum cache > sunrpc: don't immediately retransmit on seqno miss > > include/linux/sunrpc/xprt.h | 17 +++++++++++- > include/trace/events/rpcgss.h | 4 +-- > include/trace/events/sunrpc.h | 2 +- > net/sunrpc/auth_gss/auth_gss.c | 59 > ++++++++++++++++++++++++++---------------- > net/sunrpc/clnt.c | 9 +++++-- > net/sunrpc/xprt.c | 3 ++- > 6 files changed, 64 insertions(+), 30 deletions(-) > --- > base-commit: 7eb172143d5508b4da468ed59ee857c6e5e01da6 > change-id: 20250314-rfc2203-seqnum-cache-52389d14f567 > > Best regards,
This seems like a sensible thing to do to me. Acked-by: Chuck Lever <[email protected]> -- Chuck Lever
