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Commit dc6ef6be authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: do not set queue_mapping on SYNACK 



At the time of commit fff32699 ("tcp: reflect SYN queue_mapping into
SYNACK packets") we had little ways to cope with SYN floods.

We no longer need to reflect incoming skb queue mappings, and instead
can pick a TX queue based on cpu cooking the SYNACK, with normal XPS
affinities.

Note that all SYNACK retransmits were picking TX queue 0, this no longer
is a win given that SYNACK rtx are now distributed on all cpus.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 951b5d95

include/net/tcp.h

+1 −1
Original line number Diff line number Diff line
@@ -1716,7 +1716,7 @@ struct tcp_request_sock_ops { 
	__u32 (*init_seq)(const struct sk_buff *skb);

	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,

			   struct flowi *fl, struct request_sock *req,

			   u16 queue_mapping, struct tcp_fastopen_cookie *foc,

			   struct tcp_fastopen_cookie *foc,

			   bool attach_req);

};

net/ipv4/ip_output.c

+0 −1
Original line number Diff line number Diff line
@@ -1596,7 +1596,6 @@ void ip_send_unicast_reply(struct sock *sk, struct sk_buff *skb, 
			  arg->csumoffset) = csum_fold(csum_add(nskb->csum,

								arg->csum));

		nskb->ip_summed = CHECKSUM_NONE;

		skb_set_queue_mapping(nskb, skb_get_queue_mapping(skb));

		ip_push_pending_frames(sk, &fl4);

	}

out:

net/ipv4/tcp_input.c

+2 −2
Original line number Diff line number Diff line
@@ -6236,7 +6236,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, 
	}

	if (fastopen_sk) {

		af_ops->send_synack(fastopen_sk, dst, &fl, req,

				    skb_get_queue_mapping(skb), &foc, false);

				    &foc, false);

		/* Add the child socket directly into the accept queue */

		inet_csk_reqsk_queue_add(sk, req, fastopen_sk);

		sk->sk_data_ready(sk);
@@ -6247,7 +6247,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, 
		if (!want_cookie)

			inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);

		af_ops->send_synack(sk, dst, &fl, req,

				    skb_get_queue_mapping(skb), &foc, !want_cookie);

				    &foc, !want_cookie);

		if (want_cookie)

			goto drop_and_free;

	}

net/ipv4/tcp_ipv4.c

+0 −2
Original line number Diff line number Diff line
@@ -821,7 +821,6 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb, 
static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,

			      struct flowi *fl,

			      struct request_sock *req,

			      u16 queue_mapping,

			      struct tcp_fastopen_cookie *foc,

				  bool attach_req)

{
@@ -839,7 +838,6 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst, 
	if (skb) {

		__tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);



		skb_set_queue_mapping(skb, queue_mapping);

		err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,

					    ireq->ir_rmt_addr,

					    ireq->opt);

net/ipv4/tcp_output.c

+1 −1
Original line number Diff line number Diff line
@@ -3518,7 +3518,7 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req) 
	int res;



	tcp_rsk(req)->txhash = net_tx_rndhash();

	res = af_ops->send_synack(sk, NULL, &fl, req, 0, NULL, true);

	res = af_ops->send_synack(sk, NULL, &fl, req, NULL, true);

	if (!res) {

		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);

		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);