socket.7: srcfix: Add some comments on the undocumented SO_NO_CHECK option

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/socket.7 b/man7/socket.7
index bc9118bdcc2238b57567b7f9cb60658e88b486e8..24796c02c55ddb67c5b23c5254e3b3b33a8d4ea7 100644 (file)
--- a/man7/socket.7
+++ b/man7/socket.7
@@ -433,6 +433,13 @@ Otherwise, out-of-band data is passed only when the
 flag is set during receiving.
 .\" don't document it because it can do too much harm.
 .\".B SO_NO_CHECK
+.\"     The kernel has support for the SO_NO_CHECK socket
+.\"     option (boolean: 0 == default, calculate checksum on xmit,
+.\"     1 == do not calculate checksum on xmit).
+.\" Additional note from Andi Kleen on SO_NO_CHECK (2010-08-30)
+.\"     On Linux UDP checksums are essentially free and there's no reason
+.\"     to turn them off and it would disable another safety line.
+.\"     That is why I didn't document the option.
 .TP
 .B SO_PASSCRED
 Enable or disable the receiving of the