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authorAndrew Morton <akpm@osdl.org>2006-03-31 02:09:36 -0800
committerDavid S. Miller <davem@davemloft.net>2006-03-31 02:09:36 -0800
commitc08e49611a8b4e38a75bf217e1029a48faf10b82 (patch)
tree2768e4ff07657422d85d988d0f64f6f2ae8b7305 /net/core/sock.c
parent56079431b6ba163df8ba26b3eccc82379f0c0ce4 (diff)
[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: Andrew Morton <akpm@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/sock.c')
-rw-r--r--net/core/sock.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/net/core/sock.c b/net/core/sock.c
index a96ea7dd0fc..ed2afdb9ea2 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -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