net: af_unix: implement splice for stream af_unix sockets

unix_stream_recvmsg is refactored to unix_stream_read_generic in this
patch and enhanced to deal with pipe splicing. The refactoring is
inneglible, we mostly have to deal with a non-existing struct msghdr
argument.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 119 insertions, 21 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 7762c0b46721..b8c44076c776 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -520,6 +520,9 @@ static int unix_stream_sendmsg(struct socket *, struct msghdr *, size_t);
 static int unix_stream_recvmsg(struct socket *, struct msghdr *, size_t, int);
 static ssize_t unix_stream_sendpage(struct socket *, struct page *, int offset,
                                     size_t size, int flags);
+static ssize_t unix_stream_splice_read(struct socket *,  loff_t *ppos,
+                                       struct pipe_inode_info *, size_t size,
+                                       unsigned int flags);
 static int unix_dgram_sendmsg(struct socket *, struct msghdr *, size_t);
 static int unix_dgram_recvmsg(struct socket *, struct msghdr *, size_t, int);
 static int unix_dgram_connect(struct socket *, struct sockaddr *,
@@ -561,6 +564,7 @@ static const struct proto_ops unix_stream_ops = {
         .recvmsg =      unix_stream_recvmsg,
         .mmap =         sock_no_mmap,
         .sendpage =     unix_stream_sendpage,
+        .splice_read =  unix_stream_splice_read,
         .set_peek_off = unix_set_peek_off,
 };
 
@@ -1957,8 +1961,9 @@ out:
  *      Sleep until more data has arrived. But check for races..
  */
 static long unix_stream_data_wait(struct sock *sk, long timeo,
-                                  struct sk_buff *last)
+                                  struct sk_buff *last, unsigned int last_len)
 {
+        struct sk_buff *tail;
         DEFINE_WAIT(wait);
 
         unix_state_lock(sk);
@@ -1966,7 +1971,9 @@ static long unix_stream_data_wait(struct sock *sk, long timeo,
         for (;;) {
                 prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
 
-                if (skb_peek_tail(&sk->sk_receive_queue) != last ||
+                tail = skb_peek_tail(&sk->sk_receive_queue);
+                if (tail != last ||
+                    (tail && tail->len != last_len) ||
                     sk->sk_err ||
                     (sk->sk_shutdown & RCV_SHUTDOWN) ||
                     signal_pending(current) ||
@@ -1990,38 +1997,50 @@ static unsigned int unix_skb_len(const struct sk_buff *skb)
         return skb->len - UNIXCB(skb).consumed;
 }
 
-static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
-                               size_t size, int flags)
+struct unix_stream_read_state {
+        int (*recv_actor)(struct sk_buff *, int, int,
+                          struct unix_stream_read_state *);
+        struct socket *socket;
+        struct msghdr *msg;
+        struct pipe_inode_info *pipe;
+        size_t size;
+        int flags;
+        unsigned int splice_flags;
+};
+
+static int unix_stream_read_generic(struct unix_stream_read_state *state)
 {
         struct scm_cookie scm;
+        struct socket *sock = state->socket;
         struct sock *sk = sock->sk;
         struct unix_sock *u = unix_sk(sk);
-        DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr, msg->msg_name);
         int copied = 0;
+        int flags = state->flags;
         int noblock = flags & MSG_DONTWAIT;
-        int check_creds = 0;
+        bool check_creds = false;
         int target;
         int err = 0;
         long timeo;
         int skip;
+        size_t size = state->size;
+        unsigned int last_len;
 
         err = -EINVAL;
         if (sk->sk_state != TCP_ESTABLISHED)
                 goto out;
 
         err = -EOPNOTSUPP;
-        if (flags&MSG_OOB)
+        if (flags & MSG_OOB)
                 goto out;
 
-        target = sock_rcvlowat(sk, flags&MSG_WAITALL, size);
+        target = sock_rcvlowat(sk, flags & MSG_WAITALL, size);
         timeo = sock_rcvtimeo(sk, noblock);
 
+        memset(&scm, 0, sizeof(scm));
+
         /* Lock the socket to prevent queue disordering
          * while sleeps in memcpy_tomsg
          */
-
-        memset(&scm, 0, sizeof(scm));
-
         err = mutex_lock_interruptible(&u->readlock);
         if (unlikely(err)) {
                 /* recvmsg() in non blocking mode is supposed to return -EAGAIN
@@ -2037,6 +2056,7 @@ static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
 
                 unix_state_lock(sk);
                 last = skb = skb_peek(&sk->sk_receive_queue);
+                last_len = last ? last->len : 0;
 again:
                 if (skb == NULL) {
                         unix_sk(sk)->recursion_level = 0;
@@ -2059,16 +2079,17 @@ again:
                                 break;
                         mutex_unlock(&u->readlock);
 
-                        timeo = unix_stream_data_wait(sk, timeo, last);
+                        timeo = unix_stream_data_wait(sk, timeo, last,
+                                                      last_len);
 
-                        if (signal_pending(current)
-                            ||  mutex_lock_interruptible(&u->readlock)) {
+                        if (signal_pending(current) ||
+                            mutex_lock_interruptible(&u->readlock)) {
                                 err = sock_intr_errno(timeo);
                                 goto out;
                         }
 
                         continue;
- unlock:
+unlock:
                         unix_state_unlock(sk);
                         break;
                 }
@@ -2077,6 +2098,7 @@ again:
                 while (skip >= unix_skb_len(skb)) {
                         skip -= unix_skb_len(skb);
                         last = skb;
+                        last_len = skb->len;
                         skb = skb_peek_next(skb, &sk->sk_receive_queue);
                         if (!skb)
                                 goto again;
@@ -2093,18 +2115,20 @@ again:
                 } else if (test_bit(SOCK_PASSCRED, &sock->flags)) {
                         /* Copy credentials */
                         scm_set_cred(&scm, UNIXCB(skb).pid, UNIXCB(skb).uid, UNIXCB(skb).gid);
-                        check_creds = 1;
+                        check_creds = true;
                 }
 
                 /* Copy address just once */
-                if (sunaddr) {
-                        unix_copy_addr(msg, skb->sk);
+                if (state->msg && state->msg->msg_name) {
+                        DECLARE_SOCKADDR(struct sockaddr_un *, sunaddr,
+                                         state->msg->msg_name);
+                        unix_copy_addr(state->msg, skb->sk);
                         sunaddr = NULL;
                 }
 
                 chunk = min_t(unsigned int, unix_skb_len(skb) - skip, size);
-                if (skb_copy_datagram_msg(skb, UNIXCB(skb).consumed + skip,
-                                          msg, chunk)) {
+                chunk = state->recv_actor(skb, skip, chunk, state);
+                if (chunk < 0) {
                         if (copied == 0)
                                 copied = -EFAULT;
                         break;
@@ -2142,11 +2166,85 @@ again:
         } while (size);
 
         mutex_unlock(&u->readlock);
-        scm_recv(sock, msg, &scm, flags);
+        if (state->msg)
+                scm_recv(sock, state->msg, &scm, flags);
+        else
+                scm_destroy(&scm);
 out:
         return copied ? : err;
 }
 
+static int unix_stream_read_actor(struct sk_buff *skb,
+                                  int skip, int chunk,
+                                  struct unix_stream_read_state *state)
+{
+        int ret;
+
+        ret = skb_copy_datagram_msg(skb, UNIXCB(skb).consumed + skip,
+                                    state->msg, chunk);
+        return ret ?: chunk;
+}
+
+static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
+                               size_t size, int flags)
+{
+        struct unix_stream_read_state state = {
+                .recv_actor = unix_stream_read_actor,
+                .socket = sock,
+                .msg = msg,
+                .size = size,
+                .flags = flags
+        };
+
+        return unix_stream_read_generic(&state);
+}
+
+static ssize_t skb_unix_socket_splice(struct sock *sk,
+                                      struct pipe_inode_info *pipe,
+                                      struct splice_pipe_desc *spd)
+{
+        int ret;
+        struct unix_sock *u = unix_sk(sk);
+
+        mutex_unlock(&u->readlock);
+        ret = splice_to_pipe(pipe, spd);
+        mutex_lock(&u->readlock);
+
+        return ret;
+}
+
+static int unix_stream_splice_actor(struct sk_buff *skb,
+                                    int skip, int chunk,
+                                    struct unix_stream_read_state *state)
+{
+        return skb_splice_bits(skb, state->socket->sk,
+                               UNIXCB(skb).consumed + skip,
+                               state->pipe, chunk, state->splice_flags,
+                               skb_unix_socket_splice);
+}
+
+static ssize_t unix_stream_splice_read(struct socket *sock,  loff_t *ppos,
+                                       struct pipe_inode_info *pipe,
+                                       size_t size, unsigned int flags)
+{
+        struct unix_stream_read_state state = {
+                .recv_actor = unix_stream_splice_actor,
+                .socket = sock,
+                .pipe = pipe,
+                .size = size,
+                .splice_flags = flags,
+        };
+
+        if (unlikely(*ppos))
+                return -ESPIPE;
+
+        if (sock->file->f_flags & O_NONBLOCK ||
+            flags & SPLICE_F_NONBLOCK)
+                state.flags = MSG_DONTWAIT;
+
+        return unix_stream_read_generic(&state);
+}
+
 static int unix_shutdown(struct socket *sock, int mode)
 {
         struct sock *sk = sock->sk;