[PATCH] Add send(2) MSG_DONTWAIT support

[UMEZAWA Takeshi]

Hello,

I have added send(2) MSG_DONTWAIT support, which enables us to choose
nonblocking or blocking for each send(2) call.

This feature is also found in Linux.

------------------------------------------------------------------------
UMEZAWA Takeshi (FAMILY Given) <umez...@iij.ad.jp>
Internet Initiative Japan Inc.


diff --git a/lib/libc/sys/send.2 b/lib/libc/sys/send.2
index d58588f..b3b8d93 100644
--- a/lib/libc/sys/send.2
+++ b/lib/libc/sys/send.2
@@ -103,6 +103,8 @@ bypass routing, use direct interface
 .It Dv MSG_NOSIGNAL
 don't send
 .Dv SIGPIPE
+.It Dv MSG_DONTWAIT
+don't block
 .El
 .Pp
 The flag
diff --git a/sys/kern/uipc_socket.c b/sys/kern/uipc_socket.c
index 653de7d..10ef153 100644
--- a/sys/kern/uipc_socket.c
+++ b/sys/kern/uipc_socket.c
@@ -451,7 +451,7 @@ restart:
                        snderr(EMSGSIZE);
                if (space < resid + clen &&
                    (atomic || space < so->so_snd.sb_lowat || space < clen)) {
-                       if (so->so_state & SS_NBIO)
+                       if ((so->so_state & SS_NBIO) || (flags & MSG_DONTWAIT))
                                snderr(EWOULDBLOCK);
                        sbunlock(&so->so_snd);
                        error = sbwait(&so->so_snd);