From: Eric Dumazet Date: Fri, 2 Oct 2015 18:43:35 +0000 (-0700) Subject: tcp: attach SYNACK messages to request sockets instead of listener X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ca6fb06518836ef9b65dc0aac02ff97704d52a05;p=linux-beck.git tcp: attach SYNACK messages to request sockets instead of listener If a listen backlog is very big (to avoid syncookies), then the listener sk->sk_wmem_alloc is the main source of false sharing, as we need to touch it twice per SYNACK re-transmit and TX completion. (One SYN packet takes listener lock once, but up to 6 SYNACK are generated) By attaching the skb to the request socket, we remove this source of contention. Tested: listen(fd, 10485760); // single listener (no SO_REUSEPORT) 16 RX/TX queue NIC Sustain a SYNFLOOD attack of ~320,000 SYN per second, Sending ~1,400,000 SYNACK per second. Perf profiles now show listener spinlock being next bottleneck. 20.29% [kernel] [k] queued_spin_lock_slowpath 10.06% [kernel] [k] __inet_lookup_established 5.12% [kernel] [k] reqsk_timer_handler 3.22% [kernel] [k] get_next_timer_interrupt 3.00% [kernel] [k] tcp_make_synack 2.77% [kernel] [k] ipt_do_table 2.70% [kernel] [k] run_timer_softirq 2.50% [kernel] [k] ip_finish_output 2.04% [kernel] [k] cascade Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- diff --git a/include/net/tcp.h b/include/net/tcp.h index 225e9561af35..a6be56d5f0e3 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -462,7 +462,8 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len); int tcp_connect(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); + struct tcp_fastopen_cookie *foc, + bool attach_req); int tcp_disconnect(struct sock *sk, int flags); void tcp_finish_connect(struct sock *sk, struct sk_buff *skb); @@ -1715,7 +1716,8 @@ 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); + u16 queue_mapping, struct tcp_fastopen_cookie *foc, + bool attach_req); }; #ifdef CONFIG_SYN_COOKIES diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c index 80904df02187..099e0ea9242a 100644 --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -628,7 +628,7 @@ static void reqsk_queue_hash_req(struct request_sock *req, * are committed to memory and refcnt initialized. */ smp_wmb(); - atomic_set(&req->rsk_refcnt, 2); + atomic_set(&req->rsk_refcnt, 2 + 1); } void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req, diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c index f69f436fcbcc..410ac481fda0 100644 --- a/net/ipv4/tcp_fastopen.c +++ b/net/ipv4/tcp_fastopen.c @@ -161,13 +161,13 @@ static struct sock *tcp_fastopen_create_child(struct sock *sk, tp->snd_wnd = ntohs(tcp_hdr(skb)->window); /* Activate the retrans timer so that SYNACK can be retransmitted. - * The request socket is not added to the SYN table of the parent + * The request socket is not added to the ehash * because it's been added to the accept queue directly. */ inet_csk_reset_xmit_timer(child, ICSK_TIME_RETRANS, TCP_TIMEOUT_INIT, TCP_RTO_MAX); - atomic_set(&req->rsk_refcnt, 1); + atomic_set(&req->rsk_refcnt, 2); /* Add the child socket directly into the accept queue */ inet_csk_reqsk_queue_add(sk, req, child); diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index a56912772354..27108757c310 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -6120,8 +6120,6 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, struct request_sock *req; bool want_cookie = false; struct flowi fl; - int err; - /* TW buckets are converted to open requests without * limitations, they conserve resources and peer is @@ -6230,21 +6228,24 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops, tcp_rsk(req)->snt_isn = isn; tcp_rsk(req)->txhash = net_tx_rndhash(); tcp_openreq_init_rwin(req, sk, dst); - if (!want_cookie) + if (!want_cookie) { fastopen_sk = tcp_try_fastopen(sk, skb, req, &foc, dst); - err = af_ops->send_synack(fastopen_sk ?: sk, dst, &fl, req, - skb_get_queue_mapping(skb), &foc); + tcp_reqsk_record_syn(sk, req, skb); + } if (fastopen_sk) { + af_ops->send_synack(fastopen_sk, dst, &fl, req, + skb_get_queue_mapping(skb), &foc, false); sock_put(fastopen_sk); } else { - if (err || want_cookie) - goto drop_and_free; - tcp_rsk(req)->tfo_listener = false; - inet_csk_reqsk_queue_hash_add(sk, req, TCP_TIMEOUT_INIT); + 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); + if (want_cookie) + goto drop_and_free; } - tcp_reqsk_record_syn(sk, req, skb); - + reqsk_put(req); return 0; drop_and_release: diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index bfe9d39ee87d..ac2ea73e9aaf 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -822,7 +822,8 @@ 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) + struct tcp_fastopen_cookie *foc, + bool attach_req) { const struct inet_request_sock *ireq = inet_rsk(req); struct flowi4 fl4; @@ -833,7 +834,7 @@ 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); + skb = tcp_make_synack(sk, dst, req, foc, attach_req); if (skb) { __tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 09bb082ca1a7..55ed3266b05f 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -2947,7 +2947,8 @@ 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) + struct tcp_fastopen_cookie *foc, + bool attach_req) { struct inet_request_sock *ireq = inet_rsk(req); const struct tcp_sock *tp = tcp_sk(sk); @@ -2959,11 +2960,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, u16 user_mss; int mss; - /* sk is a const pointer, because we want to express multiple cpus - * might call us concurrently. - * sock_wmalloc() will change sk->sk_wmem_alloc in an atomic way. - */ - skb = sock_wmalloc((struct sock *)sk, MAX_TCP_HEADER, 1, GFP_ATOMIC); + skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); if (unlikely(!skb)) { dst_release(dst); return NULL; @@ -2971,6 +2968,17 @@ 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) { + skb->destructor = sock_edemux; + sock_hold(req_to_sk(req)); + skb->sk = req_to_sk(req); + } else { + /* 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); + } skb_dst_set(skb, dst); mss = dst_metric_advmss(dst); @@ -3510,7 +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); + res = af_ops->send_synack(sk, NULL, &fl, req, 0, NULL, true); if (!res) { TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS); NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index a215614cfb2b..3d18571811c5 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -438,7 +438,8 @@ static int tcp_v6_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) { struct inet_request_sock *ireq = inet_rsk(req); struct ipv6_pinfo *np = inet6_sk(sk); @@ -451,7 +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); + skb = tcp_make_synack(sk, dst, req, foc, attach_req); if (skb) { __tcp_v6_send_check(skb, &ireq->ir_v6_loc_addr, diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index f377702d4b91..3386cce4751e 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -224,13 +224,15 @@ static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q) if (unlikely((skb->priority & TC_PRIO_MAX) == TC_PRIO_CONTROL)) return &q->internal; - /* SYNACK messages are attached to a listener socket. - * 1) They are not part of a 'flow' yet - * 2) We do not want to rate limit them (eg SYNFLOOD attack), + /* SYNACK messages are attached to a TCP_NEW_SYN_RECV request socket + * 1) request sockets are not full blown, + * they do not contain sk_pacing_rate + * 2) They are not part of a 'flow' yet + * 3) We do not want to rate limit them (eg SYNFLOOD attack), * especially if the listener set SO_MAX_PACING_RATE - * 3) We pretend they are orphaned + * 4) We pretend they are orphaned */ - if (!sk || sk->sk_state == TCP_LISTEN) { + if (!sk || sk->sk_state == TCP_NEW_SYN_RECV) { unsigned long hash = skb_get_hash(skb) & q->orphan_mask; /* By forcing low order bit to 1, we make sure to not