BMC/Intel-BMC/linux.git/net/ipv4/inet_connection_sock.c, branch v4.4

tcp: ensure proper barriers in lockless contexts

2015-11-15T23:36:38+00:00

Some functions access TCP sockets without holding a lock and might output non consistent data, depending on compiler and or architecture. tcp_diag_get_info(), tcp_get_info(), tcp_poll(), get_tcp4_sock() ... Introduce sk_state_load() and sk_state_store() to fix the issues, and more clearly document where this lack of locking is happening. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp/dccp: fix hashdance race for passive sessions

2015-10-23T12:42:21+00:00

Multiple cpus can process duplicates of incoming ACK messages matching a SYN_RECV request socket. This is a rare event under normal operations, but definitely can happen. Only one must win the race, otherwise corruption would occur. To fix this without adding new atomic ops, we use logic in inet_ehash_nolisten() to detect the request was present in the same ehash bucket where we try to insert the new child. If request socket was not found, we have to undo the child creation. This actually removes a spin_lock()/spin_unlock() pair in reqsk_queue_unlink() for the fast path. Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets") Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp/dccp: fix race at listener dismantle phase

2015-10-16T07:52:19+00:00

Under stress, a close() on a listener can trigger the WARN_ON(sk->sk_ack_backlog) in inet_csk_listen_stop() We need to test if listener is still active before queueing a child in inet_csk_reqsk_queue_add() Create a common inet_child_forget() helper, and use it from inet_csk_reqsk_queue_add() and inet_csk_listen_stop() Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp/dccp: add inet_csk_reqsk_queue_drop_and_put() helper

2015-10-16T07:52:18+00:00

Let's reduce the confusion about inet_csk_reqsk_queue_drop() : In many cases we also need to release reference on request socket, so add a helper to do this, reducing code size and complexity. Fixes: 4bdc3d66147b ("tcp/dccp: fix behavior of stale SYN_RECV request sockets") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: avoid spurious SYN flood detection at listen() time

2015-10-15T02:06:32+00:00

At listen() time, there is a small window where listener is visible with a zero backlog, triggering a spurious "Possible SYN flooding on port" message. Nothing prevents us from setting the correct backlog. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: ensure prior synack rtx behavior with small backlogs

2015-10-07T12:08:58+00:00

Some applications use a listen() backlog of 1. Prior kernels were silently enforcing a qlen_log of 4, so that we were sending up to /proc/sys/net/ipv4/tcp_synack_retries SYNACK messages. Fixes: ef547f2ac16b ("tcp: remove max_qlen_log") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp/dccp: add a reschedule point in inet_csk_listen_stop()

2015-10-03T11:32:45+00:00

If a listener with thousands of children in accept queue is dismantled, it can take a while to close all of them. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: remove max_qlen_log

2015-10-03T11:32:44+00:00

This control variable was set at first listen(fd, backlog) call, but not updated if application tried to increase or decrease backlog. It made sense at the time listener had a non resizeable hash table. Also rounding to powers of two was not very friendly. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp/dccp: remove struct listen_sock

2015-10-03T11:32:43+00:00

It is enough to check listener sk_state, no need for an extra condition. max_qlen_log can be moved into struct request_sock_queue We can remove syn_wait_lock and the alignment it enforced. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: attach SYNACK messages to request sockets instead of listener

2015-10-03T11:32:43+00:00

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