kernel/linux.git/net/rxrpc/input.c, branch v6.18.21

rxrpc: peer->mtu_lock is redundant

2025-02-21T23:06:29+00:00

The peer->mtu_lock is only used to lock around writes to peer->max_data - and nothing else; further, all such writes take place in the I/O thread and the lock is only ever write-locked and never read-locked. In a couple of places, the write_seqcount_begin() is wrapped in preempt_disable/enable(), but not in all places. This can cause lockdep to complain: WARNING: CPU: 0 PID: 1549 at include/linux/seqlock.h:221 rxrpc_input_ack_trailer+0x305/0x430 ... RIP: 0010:rxrpc_input_ack_trailer+0x305/0x430 Fix this by just getting rid of the lock. Fixes: eeaedc5449d9 ("rxrpc: Implement path-MTU probing using padded PING ACKs (RFC8899)") Signed-off-by: David Howells cc: Marc Dionne cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250218192250.296870-3-dhowells@redhat.com Signed-off-by: Jakub Kicinski

rxrpc: Fix race in call state changing vs recvmsg()

2025-02-06T02:47:46+00:00

There's a race in between the rxrpc I/O thread recording the end of the receive phase of a call and recvmsg() examining the state of the call to determine whether it has completed. The problem is that call->_state records the I/O thread's view of the call, not the application's view (which may lag), so that alone is not sufficient. To this end, the application also checks whether there is anything left in call->recvmsg_queue for it to pick up. The call must be in state RXRPC_CALL_COMPLETE and the recvmsg_queue empty for the call to be considered fully complete. In rxrpc_input_queue_data(), the latest skbuff is added to the queue and then, if it was marked as LAST_PACKET, the state is advanced... But this is two separate operations with no locking around them. As a consequence, the lack of locking means that sendmsg() can jump into the gap on a service call and attempt to send the reply - but then get rejected because the I/O thread hasn't advanced the state yet. Simply flipping the order in which things are done isn't an option as that impacts the client side, causing the checks in rxrpc_kernel_check_life() as to whether the call is still alive to race instead. Fix this by moving the update of call->_state inside the skb queue spinlocked section where the packet is queued on the I/O thread side. rxrpc's recvmsg() will then automatically sync against this because it has to take the call->recvmsg_queue spinlock in order to dequeue the last packet. rxrpc's sendmsg() doesn't need amending as the app shouldn't be calling it to send a reply until recvmsg() indicates it has returned all of the request. Fixes: 93368b6bd58a ("rxrpc: Move call state changes from recvmsg to I/O thread") Signed-off-by: David Howells cc: Marc Dionne cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250204230558.712536-3-dhowells@redhat.com Signed-off-by: Jakub Kicinski

rxrpc: Fix call state set to not include the SERVER_SECURING state

2025-02-06T02:47:46+00:00

The RXRPC_CALL_SERVER_SECURING state doesn't really belong with the other states in the call's state set as the other states govern the call's Rx/Tx phase transition and govern when packets can and can't be received or transmitted. The "Securing" state doesn't actually govern the reception of packets and would need to be split depending on whether or not we've received the last packet yet (to mirror RECV_REQUEST/ACK_REQUEST). The "Securing" state is more about whether or not we can start forwarding packets to the application as recvmsg will need to decode them and the decoding can't take place until the challenge/response exchange has completed. Fix this by removing the RXRPC_CALL_SERVER_SECURING state from the state set and, instead, using a flag, RXRPC_CALL_CONN_CHALLENGING, to track whether or not we can queue the call for reception by recvmsg() or notify the kernel app that data is ready. In the event that we've already received all the packets, the connection event handler will poke the app layer in the appropriate manner. Also there's a race whereby the app layer sees the last packet before rxrpc has managed to end the rx phase and change the state to one amenable to allowing a reply. Fix this by queuing the packet after calling rxrpc_end_rx_phase(). Fixes: 17926a79320a ("[AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both") Signed-off-by: David Howells cc: Marc Dionne cc: Simon Horman cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20250204230558.712536-2-dhowells@redhat.com Signed-off-by: Jakub Kicinski

rxrpc: Implement RACK/TLP to deal with transmission stalls [RFC8985]

2024-12-09T21:48:33+00:00

When an rxrpc call is in its transmission phase and is sending a lot of packets, stalls occasionally occur that cause severe performance degradation (eg. increasing the transmission time for a 256MiB payload from 0.7s to 2.5s over a 10G link). rxrpc already implements TCP-style congestion control [RFC5681] and this helps mitigate the effects, but occasionally we're missing a time event that deals with a missing ACK, leading to a stall until the RTO expires. Fix this by implementing RACK/TLP in rxrpc. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Manage RTT per-call rather than per-peer

2024-12-09T21:48:32+00:00

Manage the determination of RTT on a per-call (ie. per-RPC op) basis rather than on a per-peer basis, averaging across all calls going to that peer. The problem is that the RTT measurements from the initial packets on a call may be off because the server may do some setting up (such as getting a lock on a file) before accepting the rest of the data in the RPC and, further, the RTT may be affected by server-side file operations, for instance if a large amount of data is being written or read. Note: When handling the FS.StoreData-type RPCs, for example, the server uses the userStatus field in the header of ACK packets as supplementary flow control to aid in managing this. AF_RXRPC does not yet support this, but it should be added. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Tidy up the ACK parsing a bit

2024-12-09T21:48:31+00:00

Tidy up the ACK parsing in the following ways: (1) Put the serial number of the ACK packet into the rxrpc_ack_summary struct and access it from there whilst parsing an ACK. (2) Be consistent about using "if (summary.acked_serial)" rather than "if (summary.acked_serial != 0)". Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Use irq-disabling spinlocks between app and I/O thread

2024-12-09T21:48:31+00:00

Where a spinlock is used by both the application thread and the I/O thread, use irq-disabling locking so that an interrupt taken on the app thread doesn't also slow down the I/O thread. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Send jumbo DATA packets

2024-12-09T21:48:31+00:00

Send jumbo DATA packets if the path-MTU probing using padded PING ACK packets shows up sufficient capacity to do so. This allows larger chunks of data to be sent without reducing the retryability as the subpackets in a jumbo packet can also be retransmitted individually. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Adjust the rxrpc_rtt_rx tracepoint

2024-12-09T21:48:30+00:00

Adjust the rxrpc_rtt_rx tracepoint in the following ways: (1) Display the collected RTT sample in the rxrpc_rtt_rx trace. (2) Move the division of srtt by 8 to the TP_printk() rather doing it before invoking the trace point. (3) Display the min_rtt value. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Signed-off-by: Jakub Kicinski

rxrpc: Don't use received skbuff timestamps

2024-12-09T21:48:29+00:00

Don't use received skbuff timestamps, but rather set a timestamp when an ack is processed so that the time taken to get to rxrpc_input_ack() is included in the RTT. The timestamp of the latest ACK received is tracked in call->acks_latest_ts. Signed-off-by: David Howells cc: Marc Dionne cc: linux-afs@lists.infradead.org Link: https://patch.msgid.link/20241204074710.990092-26-dhowells@redhat.com Signed-off-by: Jakub Kicinski