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.
MSG_BATCH is a performance optimization in cases where a socket
implementation can benefit by transmitting packets in a batch.
This patch also updates sendmmsg so that each contained message except
for the last one is marked as MSG_BATCH.
Signed-off-by: Tom Herbert <t...@herbertland.com>
---
include/linux/socket.h | 1 +
net/socket.c | 17 +++++++++++++----
2 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 5bf59c8..d834af2 100644
--- 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 21373f8..ef64b72 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1880,7 +1880,7 @@ static int copy_msghdr_from_user(struct msghdr *kmsg,
static int ___sys_sendmsg(struct socket *sock, struct user_msghdr __user *msg,
struct msghdr *msg_sys, unsigned int flags,
- struct used_address *used_address)
+ struct used_address *used_address, bool doing_mmsg)
{
struct compat_msghdr __user *msg_compat =
(struct compat_msghdr __user *)msg;
@@ -1906,6 +1906,8 @@ static int ___sys_sendmsg(struct socket *sock, struct
user_msghdr __user *msg,
if (msg_sys->msg_controllen > INT_MAX)
goto out_freeiov;
+ if (doing_mmsg)
+ flags |= (msg_sys->msg_flags & MSG_EOR);
ctl_len = msg_sys->msg_controllen;
if ((MSG_CMSG_COMPAT & flags) && ctl_len) {
err =
@@ -1984,7 +1986,7 @@ long __sys_sendmsg(int fd, struct user_msghdr __user
*msg, unsigned flags)
if (!sock)
goto out;
- err = ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL);
+ err = ___sys_sendmsg(sock, msg, &msg_sys, flags, NULL, false);
fput_light(sock->file, fput_needed);
out:
@@ -2011,6 +2013,7 @@ 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;
@@ -2025,11 +2028,16 @@ 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_sys, flags, &used_address,
+ true);
if (err < 0)
break;
err = __put_user(err, &compat_entry->msg_len);
@@ -2037,7 +2045,8 @@ int __sys_sendmmsg(int fd, struct mmsghdr __user *mmsg,
unsigned int vlen,
} else {
err = ___sys_sendmsg(sock,
(struct user_msghdr __user *)entry,
- &msg_sys, flags, &used_address);
+ &msg_sys, flags, &used_address,
+ true);
if (err < 0)
break;
err = put_user(err, &entry->msg_len);
--
2.4.6
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