From 8488df894d05d6fa41c2bd298c335f944bb0e401 Mon Sep 17 00:00:00 2001 From: Wei Dong Date: Fri, 2 Mar 2007 12:37:26 -0800 Subject: [PATCH] [NET]: Fix bugs in "Whether sock accept queue is full" checking when I use linux TCP socket, and find there is a bug in function sk_acceptq_is_full(). When a new SYN comes, TCP module first checks its validation. If valid, send SYN,ACK to the client and add the sock to the syn hash table. Next time if received the valid ACK for SYN,ACK from the client. server will accept this connection and increase the sk->sk_ack_backlog -- which is done in function tcp_check_req().We check wether acceptq is full in function tcp_v4_syn_recv_sock(). Consider an example: After listen(sockfd, 1) system call, sk->sk_max_ack_backlog is set to 1. As we know, sk->sk_ack_backlog is initialized to 0. Assuming accept() system call is not invoked now. 1. 1st connection comes. invoke sk_acceptq_is_full(). sk- >sk_ack_backlog=0 sk->sk_max_ack_backlog=1, function return 0 accept this connection. Increase the sk->sk_ack_backlog 2. 2nd connection comes. invoke sk_acceptq_is_full(). sk- >sk_ack_backlog=1 sk->sk_max_ack_backlog=1, function return 0 accept this connection. Increase the sk->sk_ack_backlog 3. 3rd connection comes. invoke sk_acceptq_is_full(). sk- >sk_ack_backlog=2 sk->sk_max_ack_backlog=1, function return 1. Refuse this connection. I think it has bugs. after listen system call. sk->sk_max_ack_backlog=1 but now it can accept 2 connections. Signed-off-by: Wei Dong Signed-off-by: David S. Miller --- include/net/sock.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/net/sock.h b/include/net/sock.h index 2c7d60ca3548..849c7df23181 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -426,7 +426,7 @@ static inline void sk_acceptq_added(struct sock *sk) static inline int sk_acceptq_is_full(struct sock *sk) { - return sk->sk_ack_backlog > sk->sk_max_ack_backlog; + return sk->sk_ack_backlog >= sk->sk_max_ack_backlog; } /* -- 2.20.1