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[NET]: add SO_RCVBUF comment

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

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Andrew Morton 2006-03-31 02:09:36 -08:00 committed by David S. Miller
parent 56079431b6
commit c08e49611a
1 changed files with 15 additions and 1 deletions
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16
net/core/sock.c
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@ -385,7 +385,21 @@ set_sndbuf:
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