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Commit 125c8d12 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'tcp-synflood-perf' 



Eric Dumazet says:

====================
tcp: final work on SYNFLOOD behavior

In the first patch, I remove the costly association of SYNACK+COOKIES
to a listener. I believe other parts of the stack should be ready.

The second patch removes a useless write into listener socket
in tcp_rcv_state_process(), incurring false sharing in
tcp_conn_request()

Performance under SYNFLOOD goes from 3.2 Mpps to 6 Mpps.

Test was using a single TCP listener, on a host with 8 RX queues
on the NIC, and 24 cores (48 ht)
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents ac18dd9e 8804b272

include/net/tcp.h

+7 −2
Original line number Diff line number Diff line
@@ -452,10 +452,15 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb, 
int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);

int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);

int tcp_connect(struct sock *sk);

enum tcp_synack_type {

	TCP_SYNACK_NORMAL,

	TCP_SYNACK_FASTOPEN,

	TCP_SYNACK_COOKIE,

};

struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,

				struct request_sock *req,

				struct tcp_fastopen_cookie *foc,

				bool attach_req);

				enum tcp_synack_type synack_type);

int tcp_disconnect(struct sock *sk, int flags);



void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
@@ -1728,7 +1733,7 @@ struct tcp_request_sock_ops { 
	int (*send_synack)(const struct sock *sk, struct dst_entry *dst,

			   struct flowi *fl, struct request_sock *req,

			   struct tcp_fastopen_cookie *foc,

			   bool attach_req);

			   enum tcp_synack_type synack_type);

};



#ifdef CONFIG_SYN_COOKIES

net/ipv4/tcp_input.c

+6 −5
Original line number Diff line number Diff line
@@ -5796,8 +5796,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) 
	int queued = 0;

	bool acceptable;



	tp->rx_opt.saw_tstamp = 0;



	switch (sk->sk_state) {

	case TCP_CLOSE:

		goto discard;
@@ -5838,6 +5836,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) 
		goto discard;



	case TCP_SYN_SENT:

		tp->rx_opt.saw_tstamp = 0;

		queued = tcp_rcv_synsent_state_process(sk, skb, th);

		if (queued >= 0)

			return queued;
@@ -5849,6 +5848,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb) 
		return 0;

	}



	tp->rx_opt.saw_tstamp = 0;

	req = tp->fastopen_rsk;

	if (req) {

		WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV &&
@@ -6327,7 +6327,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, 
	}

	if (fastopen_sk) {

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

				    &foc, false);

				    &foc, TCP_SYNACK_FASTOPEN);

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

		inet_csk_reqsk_queue_add(sk, req, fastopen_sk);

		sk->sk_data_ready(sk);
@@ -6337,8 +6337,9 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, 
		tcp_rsk(req)->tfo_listener = false;

		if (!want_cookie)

			inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT);

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

				    &foc, !want_cookie);

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

				    !want_cookie ? TCP_SYNACK_NORMAL :

						   TCP_SYNACK_COOKIE);

		if (want_cookie) {

			reqsk_free(req);

			return 0;

net/ipv4/tcp_ipv4.c

+2 −2
Original line number Diff line number Diff line
@@ -830,7 +830,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst, 
			      struct flowi *fl,

			      struct request_sock *req,

			      struct tcp_fastopen_cookie *foc,

				  bool attach_req)

			      enum tcp_synack_type synack_type)

{

	const struct inet_request_sock *ireq = inet_rsk(req);

	struct flowi4 fl4;
@@ -841,7 +841,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst, 
	if (!dst && (dst = inet_csk_route_req(sk, &fl4, req)) == NULL)

		return -1;



	skb = tcp_make_synack(sk, dst, req, foc, attach_req);

	skb = tcp_make_synack(sk, dst, req, foc, synack_type);



	if (skb) {

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

net/ipv4/tcp_output.c

+12 −4
Original line number Diff line number Diff line
@@ -2944,7 +2944,7 @@ int tcp_send_synack(struct sock *sk) 
struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst,

				struct request_sock *req,

				struct tcp_fastopen_cookie *foc,

				bool attach_req)

				enum tcp_synack_type synack_type)

{

	struct inet_request_sock *ireq = inet_rsk(req);

	const struct tcp_sock *tp = tcp_sk(sk);
@@ -2964,14 +2964,22 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, 
	/* Reserve space for headers. */

	skb_reserve(skb, MAX_TCP_HEADER);



	if (attach_req) {

	switch (synack_type) {

	case TCP_SYNACK_NORMAL:

		skb_set_owner_w(skb, req_to_sk(req));

	} else {

		break;

	case TCP_SYNACK_COOKIE:

		/* Under synflood, we do not attach skb to a socket,

		 * to avoid false sharing.

		 */

		break;

	case TCP_SYNACK_FASTOPEN:

		/* sk is a const pointer, because we want to express multiple

		 * cpu might call us concurrently.

		 * sk->sk_wmem_alloc in an atomic, we can promote to rw.

		 */

		skb_set_owner_w(skb, (struct sock *)sk);

		break;

	}

	skb_dst_set(skb, dst);
@@ -3516,7 +3524,7 @@ 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, NULL, true);

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

	if (!res) {

		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS);

		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);

net/ipv6/tcp_ipv6.c

+2 −2
Original line number Diff line number Diff line
@@ -439,7 +439,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst, 
			      struct flowi *fl,

			      struct request_sock *req,

			      struct tcp_fastopen_cookie *foc,

			      bool attach_req)

			      enum tcp_synack_type synack_type)

{

	struct inet_request_sock *ireq = inet_rsk(req);

	struct ipv6_pinfo *np = inet6_sk(sk);
@@ -452,7 +452,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst, 
					       IPPROTO_TCP)) == NULL)

		goto done;



	skb = tcp_make_synack(sk, dst, req, foc, attach_req);

	skb = tcp_make_synack(sk, dst, req, foc, synack_type);



	if (skb) {

		__tcp_v6_send_check(skb, &ireq->ir_v6_loc_addr,