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Commit c08e4961 authored by Andrew Morton's avatar Andrew Morton Committed by David S. Miller
Browse files

[NET]: add SO_RCVBUF comment 



Put a comment in there explaining why we double the setsockopt()
caller's SO_RCVBUF.  People keep wondering.

Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 56079431

net/core/sock.c

+15 −1
Original line number Diff line number Diff line
@@ -385,7 +385,21 @@ int sock_setsockopt(struct socket *sock, int level, int optname, 
				val = sysctl_rmem_max;

set_rcvbuf:

			sk->sk_userlocks |= SOCK_RCVBUF_LOCK;

			/* FIXME: is this lower bound the right one? */

			/*

			 * We double it on the way in to account for

			 * "struct sk_buff" etc. overhead.   Applications

			 * assume that the SO_RCVBUF setting they make will

			 * allow that much actual data to be received on that

			 * socket.

			 *

			 * Applications are unaware that "struct sk_buff" and

			 * other overheads allocate from the receive buffer

			 * during socket buffer allocation.

			 *

			 * And after considering the possible alternatives,

			 * returning the value we actually used in getsockopt

			 * is the most desirable behavior.

			 */

			if ((val * 2) < SOCK_MIN_RCVBUF)

				sk->sk_rcvbuf = SOCK_MIN_RCVBUF;

			else