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>

1 files changed, 183 insertions, 42 deletions

diff --git a/net/socket.c b/net/socket.c
index 807935693846..9dff31c9b799 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -683,10 +683,9 @@ void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
 }
 EXPORT_SYMBOL_GPL(sock_recv_ts_and_drops);
 
-static inline int __sock_recvmsg(struct kiocb *iocb, struct socket *sock,
-                                 struct msghdr *msg, size_t size, int flags)
+static inline int __sock_recvmsg_nosec(struct kiocb *iocb, struct socket *sock,
+                                       struct msghdr *msg, size_t size, int flags)
 {
-        int err;
         struct sock_iocb *si = kiocb_to_siocb(iocb);
 
         si->sock = sock;
@@ -695,13 +694,17 @@ static inline int __sock_recvmsg(struct kiocb *iocb, struct socket *sock,
         si->size = size;
         si->flags = flags;
 
-        err = security_socket_recvmsg(sock, msg, size, flags);
-        if (err)
-                return err;
-
         return sock->ops->recvmsg(iocb, sock, msg, size, flags);
 }
 
+static inline int __sock_recvmsg(struct kiocb *iocb, struct socket *sock,
+                                 struct msghdr *msg, size_t size, int flags)
+{
+        int err = security_socket_recvmsg(sock, msg, size, flags);
+
+        return err ?: __sock_recvmsg_nosec(iocb, sock, msg, size, flags);
+}
+
 int sock_recvmsg(struct socket *sock, struct msghdr *msg,
                  size_t size, int flags)
 {
@@ -717,6 +720,21 @@ int sock_recvmsg(struct socket *sock, struct msghdr *msg,
         return ret;
 }
 
+static int sock_recvmsg_nosec(struct socket *sock, struct msghdr *msg,
+                              size_t size, int flags)
+{
+        struct kiocb iocb;
+        struct sock_iocb siocb;
+        int ret;
+
+        init_sync_kiocb(&iocb, NULL);
+        iocb.private = &siocb;
+        ret = __sock_recvmsg_nosec(&iocb, sock, msg, size, flags);
+        if (-EIOCBQUEUED == ret)
+                ret = wait_on_sync_kiocb(&iocb);
+        return ret;
+}
+
 int kernel_recvmsg(struct socket *sock, struct msghdr *msg,
                    struct kvec *vec, size_t num, size_t size, int flags)
 {
@@ -1983,22 +2001,15 @@ out:
         return err;
 }
 
-/*
- *      BSD recvmsg interface
- */
-
-SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
-                unsigned int, flags)
+static int __sys_recvmsg(struct socket *sock, struct msghdr __user *msg,
+                         struct msghdr *msg_sys, unsigned flags, int nosec)
 {
         struct compat_msghdr __user *msg_compat =
             (struct compat_msghdr __user *)msg;
-        struct socket *sock;
         struct iovec iovstack[UIO_FASTIOV];
         struct iovec *iov = iovstack;
-        struct msghdr msg_sys;
         unsigned long cmsg_ptr;
         int err, iov_size, total_len, len;
-        int fput_needed;
 
         /* kernel mode address */
         struct sockaddr_storage addr;
@@ -2008,27 +2019,23 @@ SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
         int __user *uaddr_len;
 
         if (MSG_CMSG_COMPAT & flags) {
-                if (get_compat_msghdr(&msg_sys, msg_compat))
+                if (get_compat_msghdr(msg_sys, msg_compat))
                         return -EFAULT;
         }
-        else if (copy_from_user(&msg_sys, msg, sizeof(struct msghdr)))
+        else if (copy_from_user(msg_sys, msg, sizeof(struct msghdr)))
                 return -EFAULT;
 
-        sock = sockfd_lookup_light(fd, &err, &fput_needed);
-        if (!sock)
-                goto out;
-
         err = -EMSGSIZE;
-        if (msg_sys.msg_iovlen > UIO_MAXIOV)
-                goto out_put;
+        if (msg_sys->msg_iovlen > UIO_MAXIOV)
+                goto out;
 
         /* Check whether to allocate the iovec area */
         err = -ENOMEM;
-        iov_size = msg_sys.msg_iovlen * sizeof(struct iovec);
-        if (msg_sys.msg_iovlen > UIO_FASTIOV) {
+        iov_size = msg_sys->msg_iovlen * sizeof(struct iovec);
+        if (msg_sys->msg_iovlen > UIO_FASTIOV) {
                 iov = sock_kmalloc(sock->sk, iov_size, GFP_KERNEL);
                 if (!iov)
-                        goto out_put;
+                        goto out;
         }
 
         /*
@@ -2036,46 +2043,47 @@ SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
          *      kernel msghdr to use the kernel address space)
          */
 
-        uaddr = (__force void __user *)msg_sys.msg_name;
+        uaddr = (__force void __user *)msg_sys->msg_name;
         uaddr_len = COMPAT_NAMELEN(msg);
         if (MSG_CMSG_COMPAT & flags) {
-                err = verify_compat_iovec(&msg_sys, iov,
+                err = verify_compat_iovec(msg_sys, iov,
                                           (struct sockaddr *)&addr,
                                           VERIFY_WRITE);
         } else
-                err = verify_iovec(&msg_sys, iov,
+                err = verify_iovec(msg_sys, iov,
                                    (struct sockaddr *)&addr,
                                    VERIFY_WRITE);
         if (err < 0)
                 goto out_freeiov;
         total_len = err;
 
-        cmsg_ptr = (unsigned long)msg_sys.msg_control;
-        msg_sys.msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);
+        cmsg_ptr = (unsigned long)msg_sys->msg_control;
+        msg_sys->msg_flags = flags & (MSG_CMSG_CLOEXEC|MSG_CMSG_COMPAT);
 
         if (sock->file->f_flags & O_NONBLOCK)
                 flags |= MSG_DONTWAIT;
-        err = sock_recvmsg(sock, &msg_sys, total_len, flags);
+        err = (nosec ? sock_recvmsg_nosec : sock_recvmsg)(sock, msg_sys,
+                                                          total_len, flags);
         if (err < 0)
                 goto out_freeiov;
         len = err;
 
         if (uaddr != NULL) {
                 err = move_addr_to_user((struct sockaddr *)&addr,
-                                        msg_sys.msg_namelen, uaddr,
+                                        msg_sys->msg_namelen, uaddr,
                                         uaddr_len);
                 if (err < 0)
                         goto out_freeiov;
         }
-        err = __put_user((msg_sys.msg_flags & ~MSG_CMSG_COMPAT),
+        err = __put_user((msg_sys->msg_flags & ~MSG_CMSG_COMPAT),
                          COMPAT_FLAGS(msg));
         if (err)
                 goto out_freeiov;
         if (MSG_CMSG_COMPAT & flags)
-                err = __put_user((unsigned long)msg_sys.msg_control - cmsg_ptr,
+                err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
                                  &msg_compat->msg_controllen);
         else
-                err = __put_user((unsigned long)msg_sys.msg_control - cmsg_ptr,
+                err = __put_user((unsigned long)msg_sys->msg_control - cmsg_ptr,
                                  &msg->msg_controllen);
         if (err)
                 goto out_freeiov;
@@ -2084,21 +2092,150 @@ SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
 out_freeiov:
         if (iov != iovstack)
                 sock_kfree_s(sock->sk, iov, iov_size);
-out_put:
+out:
+        return err;
+}
+
+/*
+ *      BSD recvmsg interface
+ */
+
+SYSCALL_DEFINE3(recvmsg, int, fd, struct msghdr __user *, msg,
+                unsigned int, flags)
+{
+        int fput_needed, err;
+        struct msghdr msg_sys;
+        struct socket *sock = sockfd_lookup_light(fd, &err, &fput_needed);
+
+        if (!sock)
+                goto out;
+
+        err = __sys_recvmsg(sock, msg, &msg_sys, flags, 0);
+
         fput_light(sock->file, fput_needed);
 out:
         return err;
 }
 
-#ifdef __ARCH_WANT_SYS_SOCKETCALL
+/*
+ *     Linux recvmmsg interface
+ */
+
+int __sys_recvmmsg(int fd, struct mmsghdr __user *mmsg, unsigned int vlen,
+                   unsigned int flags, struct timespec *timeout)
+{
+        int fput_needed, err, datagrams;
+        struct socket *sock;
+        struct mmsghdr __user *entry;
+        struct msghdr msg_sys;
+        struct timespec end_time;
+
+        if (timeout &&
+            poll_select_set_timeout(&end_time, timeout->tv_sec,
+                                    timeout->tv_nsec))
+                return -EINVAL;
+
+        datagrams = 0;
+
+        sock = sockfd_lookup_light(fd, &err, &fput_needed);
+        if (!sock)
+                return err;
+
+        err = sock_error(sock->sk);
+        if (err)
+                goto out_put;
+
+        entry = mmsg;
+
+        while (datagrams < vlen) {
+                /*
+                 * No need to ask LSM for more than the first datagram.
+                 */
+                err = __sys_recvmsg(sock, (struct msghdr __user *)entry,
+                                    &msg_sys, flags, datagrams);
+                if (err < 0)
+                        break;
+                err = put_user(err, &entry->msg_len);
+                if (err)
+                        break;
+                ++entry;
+                ++datagrams;
+
+                if (timeout) {
+                        ktime_get_ts(timeout);
+                        *timeout = timespec_sub(end_time, *timeout);
+                        if (timeout->tv_sec < 0) {
+                                timeout->tv_sec = timeout->tv_nsec = 0;
+                                break;
+                        }
+
+                        /* Timeout, return less than vlen datagrams */
+                        if (timeout->tv_nsec == 0 && timeout->tv_sec == 0)
+                                break;
+                }
+
+                /* Out of band data, return right away */
+                if (msg_sys.msg_flags & MSG_OOB)
+                        break;
+        }
+
+out_put:
+        fput_light(sock->file, fput_needed);
 
+        if (err == 0)
+                return datagrams;
+
+        if (datagrams != 0) {
+                /*
+                 * We may return less entries than requested (vlen) if the
+                 * sock is non block and there aren't enough datagrams...
+                 */
+                if (err != -EAGAIN) {
+                        /*
+                         * ... or  if recvmsg returns an error after we
+                         * received some datagrams, where we record the
+                         * error to return on the next call or if the
+                         * app asks about it using getsockopt(SO_ERROR).
+                         */
+                        sock->sk->sk_err = -err;
+                }
+
+                return datagrams;
+        }
+
+        return err;
+}
+
+SYSCALL_DEFINE5(recvmmsg, int, fd, struct mmsghdr __user *, mmsg,
+                unsigned int, vlen, unsigned int, flags,
+                struct timespec __user *, timeout)
+{
+        int datagrams;
+        struct timespec timeout_sys;
+
+        if (!timeout)
+                return __sys_recvmmsg(fd, mmsg, vlen, flags, NULL);
+
+        if (copy_from_user(&timeout_sys, timeout, sizeof(timeout_sys)))
+                return -EFAULT;
+
+        datagrams = __sys_recvmmsg(fd, mmsg, vlen, flags, &timeout_sys);
+
+        if (datagrams > 0 &&
+            copy_to_user(timeout, &timeout_sys, sizeof(timeout_sys)))
+                datagrams = -EFAULT;
+
+        return datagrams;
+}
+
+#ifdef __ARCH_WANT_SYS_SOCKETCALL
 /* Argument list sizes for sys_socketcall */
 #define AL(x) ((x) * sizeof(unsigned long))
-static const unsigned char nargs[19]={
+static const unsigned char nargs[20] = {
         AL(0),AL(3),AL(3),AL(3),AL(2),AL(3),
         AL(3),AL(3),AL(4),AL(4),AL(4),AL(6),
         AL(6),AL(2),AL(5),AL(5),AL(3),AL(3),
-        AL(4)
+        AL(4),AL(5)
 };
 
 #undef AL
@@ -2118,7 +2255,7 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
         int err;
         unsigned int len;
 
-        if (call < 1 || call > SYS_ACCEPT4)
+        if (call < 1 || call > SYS_RECVMMSG)
                 return -EINVAL;
 
         len = nargs[call];
@@ -2196,6 +2333,10 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
         case SYS_RECVMSG:
                 err = sys_recvmsg(a0, (struct msghdr __user *)a1, a[2]);
                 break;
+        case SYS_RECVMMSG:
+                err = sys_recvmmsg(a0, (struct mmsghdr __user *)a1, a[2], a[3],
+                                   (struct timespec __user *)a[4]);
+                break;
         case SYS_ACCEPT4:
                 err = sys_accept4(a0, (struct sockaddr __user *)a1,
                                   (int __user *)a[2], a[3]);