| From: |
| Brandon L Black <blblack@gmail.com> |
| To: |
| netdev@vger.kernel.org |
| Subject: |
| [PATCH] Add MSG_WAITFORONE flag to recvmmsg |
| Date: |
| Fri, 26 Mar 2010 17:35:30 -0500 |
| Message-ID: |
| <20100326223530.GA11817@xpc.home> |
| Cc: |
| "David S. Miller" <davem@davemloft.net>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
Ulrich Drepper <drepper@gmail.com>,
linux-kernel@vger.kernel.org |
| Archive‑link: | |
Article |
From: Brandon L Black <blblack@gmail.com>
Add new flag MSG_WAITFORONE for the recvmmsg() syscall.
When this flag is specified for a blocking socket, recvmmsg()
will only block until at least 1 packet is available. The
default behavior is to block until all vlen packets are
available. This flag has no effect on non-blocking sockets
or when used in combination with MSG_DONTWAIT.
Signed-off-by: Brandon L Black <blblack@gmail.com>
---
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 7b3aae2..354cc56 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -255,6 +255,7 @@ struct ucred {
#define MSG_ERRQUEUE 0x2000 /* Fetch message from error queue */
#define MSG_NOSIGNAL 0x4000 /* Do not generate SIGPIPE */
#define MSG_MORE 0x8000 /* Sender will send more */
+#define MSG_WAITFORONE 0x10000 /* recvmmsg(): block until 1+ packets avail */
#define MSG_EOF MSG_FIN
diff --git a/net/socket.c b/net/socket.c
index 769c386..33304d1 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2133,7 +2133,10 @@ int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
if (err)
break;
- ++datagrams;
+
+ /* MSG_WAITFORONE turns on MSG_DONTWAIT after one packet */
+ if (!datagrams++ && (flags & MSG_WAITFORONE))
+ flags |= MSG_DONTWAIT;
if (timeout) {
ktime_get_ts(timeout);
--
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