net: Add MSG_BATCH flag

Add a new msg flag called MSG_BATCH. This flag is used in sendmsg to
indicate that more messages will follow (i.e. a batch of messages is
being sent). This is similar to MSG_MORE except that the following
messages are not merged into one packet, they are sent individually.
sendmmsg is updated so that each contained message except for the
last one is marked as MSG_BATCH.

MSG_BATCH is a performance optimization in cases where a socket
implementation can benefit by transmitting packets in a batch.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 5bf59c8493b763c6dc11ccce18da9c0ac6c0da46..d834af22a4607cd2acfd69490f891e13690c7bae 100644 (file)
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -274,6 +274,7 @@ struct ucred {
 #define MSG_MORE       0x8000  /* Sender will send more */
 #define MSG_WAITFORONE 0x10000 /* recvmmsg(): block until 1+ packets avail */
 #define MSG_SENDPAGE_NOTLAST 0x20000 /* sendpage() internal : not the last page */
+#define MSG_BATCH      0x40000 /* sendmmsg(): more messages coming */
 #define MSG_EOF         MSG_FIN
 
 #define MSG_FASTOPEN   0x20000000      /* Send data in TCP SYN */

diff --git a/net/socket.c b/net/socket.c
index 0dd4dd818f41ffcb1b5c36921680f0fdff46bde2..886649c88d8f4c2e004e11de26e7bafdfec91760 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -2008,6 +2008,7 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
        struct compat_mmsghdr __user *compat_entry;
        struct msghdr msg_sys;
        struct used_address used_address;
+       unsigned int oflags = flags;
 
        if (vlen > UIO_MAXIOV)
                vlen = UIO_MAXIOV;
@@ -2022,8 +2023,12 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
        entry = mmsg;
        compat_entry = (struct compat_mmsghdr __user *)mmsg;
        err = 0;
+       flags |= MSG_BATCH;
 
        while (datagrams < vlen) {
+               if (datagrams == vlen - 1)
+                       flags = oflags;
+
                if (MSG_CMSG_COMPAT & flags) {
                        err = ___sys_sendmsg(sock, (struct user_msghdr __user *)compat_entry,
                                             &msg_sys, flags, &used_address, MSG_EOR);