From 2aeef18d37aa8c0bfca169d4ede1790d972bf649 Mon Sep 17 00:00:00 2001 From: Nivedita Singhvi Date: Mon, 28 Jan 2013 17:52:37 +0000 Subject: tcp: Increment LISTENOVERFLOW and LISTENDROPS in tcp_v4_conn_request() We drop a connection request if the accept backlog is full and there are sufficient packets in the syn queue to warrant starting drops. Increment the appropriate counters so this isn't silent, for accurate stats and help in debugging. This patch assumes LINUX_MIB_LISTENDROPS is a superset of/includes the counter LINUX_MIB_LISTENOVERFLOWS. Signed-off-by: Nivedita Singhvi Acked-by: Vijay Subramanian Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 70b09ef2463b..629937d514eb 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1500,8 +1500,11 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) * clogging syn queue with openreqs with exponentially increasing * timeout. */ - if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) + if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) { + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS); goto drop; + } req = inet_reqsk_alloc(&tcp_request_sock_ops); if (!req) -- cgit v1.2.3 From 66555e92fb7a619188c02cceae4bbc414f15f96d Mon Sep 17 00:00:00 2001 From: Yuchung Cheng Date: Thu, 31 Jan 2013 11:16:46 -0800 Subject: tcp: detect SYN/data drop when F-RTO is disabled On receiving the SYN-ACK, Fast Open checks icsk_retransmit for SYN retransmission to detect SYN/data drops. But if F-RTO is disabled, icsk_retransmit is reset at step D of tcp_fastretrans_alert() ( under tcp_ack()) before tcp_rcv_fastopen_synack(). The fix is to use total_retrans instead which accounts for SYN retransmission regardless the use of F-RTO. Signed-off-by: Yuchung Cheng Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 18f97ca76b00..8aca4ee95ff9 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5649,8 +5649,7 @@ static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack, * the remote receives only the retransmitted (regular) SYNs: either * the original SYN-data or the corresponding SYN-ACK is lost. */ - syn_drop = (cookie->len <= 0 && data && - inet_csk(sk)->icsk_retransmits); + syn_drop = (cookie->len <= 0 && data && tp->total_retrans); tcp_fastopen_cache_set(sk, mss, cookie, syn_drop); -- cgit v1.2.3 From 973ec449bb4f2b8c514bacbcb4d9506fc31c8ce3 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 2 Feb 2013 05:23:16 +0000 Subject: tcp: fix an infinite loop in tcp_slow_start() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Since commit 9dc274151a548 (tcp: fix ABC in tcp_slow_start()), a nul snd_cwnd triggers an infinite loop in tcp_slow_start() Avoid this infinite loop and log a one time error for further analysis. FRTO code is suspected to cause this bug. Reported-by: Pasi Kärkkäinen Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Signed-off-by: David S. Miller --- net/ipv4/tcp_cong.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 291f2ed7cc31..cdf2e707bb10 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -310,6 +310,12 @@ void tcp_slow_start(struct tcp_sock *tp) { int cnt; /* increase in packets */ unsigned int delta = 0; + u32 snd_cwnd = tp->snd_cwnd; + + if (unlikely(!snd_cwnd)) { + pr_err_once("snd_cwnd is nul, please report this bug.\n"); + snd_cwnd = 1U; + } /* RFC3465: ABC Slow start * Increase only after a full MSS of bytes is acked @@ -324,7 +330,7 @@ void tcp_slow_start(struct tcp_sock *tp) if (sysctl_tcp_max_ssthresh > 0 && tp->snd_cwnd > sysctl_tcp_max_ssthresh) cnt = sysctl_tcp_max_ssthresh >> 1; /* limited slow start */ else - cnt = tp->snd_cwnd; /* exponential increase */ + cnt = snd_cwnd; /* exponential increase */ /* RFC3465: ABC * We MAY increase by 2 if discovered delayed ack @@ -334,11 +340,11 @@ void tcp_slow_start(struct tcp_sock *tp) tp->bytes_acked = 0; tp->snd_cwnd_cnt += cnt; - while (tp->snd_cwnd_cnt >= tp->snd_cwnd) { - tp->snd_cwnd_cnt -= tp->snd_cwnd; + while (tp->snd_cwnd_cnt >= snd_cwnd) { + tp->snd_cwnd_cnt -= snd_cwnd; delta++; } - tp->snd_cwnd = min(tp->snd_cwnd + delta, tp->snd_cwnd_clamp); + tp->snd_cwnd = min(snd_cwnd + delta, tp->snd_cwnd_clamp); } EXPORT_SYMBOL_GPL(tcp_slow_start); -- cgit v1.2.3 From 2e5f421211ff76c17130b4597bc06df4eeead24f Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 3 Feb 2013 09:13:05 +0000 Subject: tcp: frto should not set snd_cwnd to 0 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Commit 9dc274151a548 (tcp: fix ABC in tcp_slow_start()) uncovered a bug in FRTO code : tcp_process_frto() is setting snd_cwnd to 0 if the number of in flight packets is 0. As Neal pointed out, if no packet is in flight we lost our chance to disambiguate whether a loss timeout was spurious. We should assume it was a proper loss. Reported-by: Pasi Kärkkäinen Signed-off-by: Neal Cardwell Signed-off-by: Eric Dumazet Cc: Ilpo Järvinen Cc: Yuchung Cheng Signed-off-by: David S. Miller --- net/ipv4/tcp_input.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 8aca4ee95ff9..680c4224ed96 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3484,7 +3484,8 @@ static bool tcp_process_frto(struct sock *sk, int flag) ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED))) tp->undo_marker = 0; - if (!before(tp->snd_una, tp->frto_highmark)) { + if (!before(tp->snd_una, tp->frto_highmark) || + !tcp_packets_in_flight(tp)) { tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); return true; } -- cgit v1.2.3 From 848bf15f361c7c22da7998c81d50ed3dffbc827d Mon Sep 17 00:00:00 2001 From: Vijay Subramanian Date: Thu, 31 Jan 2013 08:24:06 +0000 Subject: tcp: Update MIB counters for drops This patch updates LINUX_MIB_LISTENDROPS in tcp_v4_conn_request() and tcp_v4_err(). tcp_v4_conn_request() in particular can drop SYNs for various reasons which are not currently tracked. Signed-off-by: Vijay Subramanian Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 629937d514eb..eadb693eef55 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -496,6 +496,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info) * errors returned from accept(). */ inet_csk_reqsk_queue_drop(sk, req, prev); + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS); goto out; case TCP_SYN_SENT: @@ -1502,7 +1503,6 @@ int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb) */ if (sk_acceptq_is_full(sk) && inet_csk_reqsk_queue_young(sk) > 1) { NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS); - NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS); goto drop; } @@ -1669,6 +1669,7 @@ drop_and_release: drop_and_free: reqsk_free(req); drop: + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS); return 0; } EXPORT_SYMBOL(tcp_v4_conn_request); -- cgit v1.2.3