net: Introduce recvmmsg socket syscall
Meaning receive multiple messages, reducing the number of syscalls and
net stack entry/exit operations.
Next patches will introduce mechanisms where protocols that want to
optimize this operation will provide an unlocked_recvmsg operation.
This takes into account comments made by:
. Paul Moore: sock_recvmsg is called only for the first datagram,
sock_recvmsg_nosec is used for the rest.
. Caitlin Bestler: recvmmsg now has a struct timespec timeout, that
works in the same fashion as the ppoll one.
If the underlying protocol returns a datagram with MSG_OOB set, this
will make recvmmsg return right away with as many datagrams (+ the OOB
one) it has received so far.
. Rémi Denis-Courmont & Steven Whitehouse: If we receive N < vlen
datagrams and then recvmsg returns an error, recvmmsg will return
the successfully received datagrams, store the error and return it
in the next call.
This paves the way for a subsequent optimization, sk_prot->unlocked_recvmsg,
where we will be able to acquire the lock only at batch start and end, not at
every underlying recvmsg call.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/compat.h b/include/net/compat.h
index 7c30028..9679f05 100644
--- a/include/net/compat.h
+++ b/include/net/compat.h
@@ -18,6 +18,11 @@
compat_uint_t msg_flags;
};
+struct compat_mmsghdr {
+ struct compat_msghdr msg_hdr;
+ compat_uint_t msg_len;
+};
+
struct compat_cmsghdr {
compat_size_t cmsg_len;
compat_int_t cmsg_level;
@@ -35,6 +40,9 @@
extern int verify_compat_iovec(struct msghdr *, struct iovec *, struct sockaddr *, int);
extern asmlinkage long compat_sys_sendmsg(int,struct compat_msghdr __user *,unsigned);
extern asmlinkage long compat_sys_recvmsg(int,struct compat_msghdr __user *,unsigned);
+extern asmlinkage long compat_sys_recvmmsg(int, struct compat_mmsghdr __user *,
+ unsigned, unsigned,
+ struct timespec __user *);
extern asmlinkage long compat_sys_getsockopt(int, int, int, char __user *, int __user *);
extern int put_cmsg_compat(struct msghdr*, int, int, int, void *);
