From 5487796f0c9475586277a0a7a91211ce5746fa6a Mon Sep 17 00:00:00 2001 From: Sam Jansen Date: Mon, 19 Nov 2007 23:28:21 -0800 Subject: [PATCH] [TCP]: Problem bug with sysctl_tcp_congestion_control function From: "Sam Jansen" sysctl_tcp_congestion_control seems to have a bug that prevents it from actually calling the tcp_set_default_congestion_control function. This is not so apparent because it does not return an error and generally the /proc interface is used to configure the default TCP congestion control algorithm. This is present in 2.6.18 onwards and probably earlier, though I have not inspected 2.6.15--2.6.17. sysctl_tcp_congestion_control calls sysctl_string and expects a successful return code of 0. In such a case it actually sets the congestion control algorithm with tcp_set_default_congestion_control. Otherwise, it returns the value returned by sysctl_string. This was correct in 2.6.14, as sysctl_string returned 0 on success. However, sysctl_string was updated to return 1 on success around about 2.6.15 and sysctl_tcp_congestion_control was not updated. Even though sysctl_tcp_congestion_control returns 1, do_sysctl_strategy converts this return code to '0', so the caller never notices the error. Signed-off-by: David S. Miller --- net/ipv4/sysctl_net_ipv4.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index ffddd2b453..bec6fe8806 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -191,7 +191,7 @@ static int sysctl_tcp_congestion_control(ctl_table *table, int __user *name, tcp_get_default_congestion_control(val); ret = sysctl_string(&tbl, name, nlen, oldval, oldlenp, newval, newlen); - if (ret == 0 && newval && newlen) + if (ret == 1 && newval && newlen) ret = tcp_set_default_congestion_control(val); return ret; } -- 2.39.5