Mon, Jun 17, 2024 at 09:56:40AM CEST, luoxuanqiang@xxxxxxxxxx wrote: >When bonding is configured in BOND_MODE_BROADCAST mode, if two identical >SYN packets are received at the same time and processed on different CPUs, >it can potentially create the same sk (sock) but two different reqsk >(request_sock) in tcp_conn_request(). > >These two different reqsk will respond with two SYNACK packets, and since >the generation of the seq (ISN) incorporates a timestamp, the final two >SYNACK packets will have different seq values. > >The consequence is that when the Client receives and replies with an ACK >to the earlier SYNACK packet, we will reset(RST) it. > >======================================================================== > >This behavior is consistently reproducible in my local setup, >which comprises: > > | NETA1 ------ NETB1 | >PC_A --- bond --- | | --- bond --- PC_B > | NETA2 ------ NETB2 | > >- PC_A is the Server and has two network cards, NETA1 and NETA2. I have > bonded these two cards using BOND_MODE_BROADCAST mode and configured > them to be handled by different CPU. > >- PC_B is the Client, also equipped with two network cards, NETB1 and > NETB2, which are also bonded and configured in BOND_MODE_BROADCAST mode. > >If the client attempts a TCP connection to the server, it might encounter >a failure. Capturing packets from the server side reveals: > >10.10.10.10.45182 > localhost: Flags [S], seq 320236027, >10.10.10.10.45182 > localhost: Flags [S], seq 320236027, >localhost > 10.10.10.10.45182: Flags [S.], seq 2967855116, >localhost > 10.10.10.10.45182: Flags [S.], seq 2967855123, <== >10.10.10.10.45182 > localhost: Flags [.], ack 4294967290, >10.10.10.10.45182 > localhost: Flags [.], ack 4294967290, >localhost > 10.10.10.10.45182: Flags [R], seq 2967855117, <== >localhost > 10.10.10.10.45182: Flags [R], seq 2967855117, > >Two SYNACKs with different seq numbers are sent by localhost, >resulting in an anomaly. > >======================================================================== > >The attempted solution is as follows: >In the tcp_conn_request(), while inserting reqsk into the ehash table, >it also checks if an entry already exists. If found, it avoids >reinsertion and releases it. > >Simultaneously, In the reqsk_queue_hash_req(), the start of the >req->rsk_timer is adjusted to be after successful insertion. > >Signed-off-by: luoxuanqiang <luoxuanqiang@xxxxxxxxxx> You are missing "Fixes" tag.
