tipc: refactor function tipc_sk_recvmsg()

We try to make this function more readable by improving variable names
and comments, plus some minor changes to the logics.

Reviewed-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 8a4e9fe5f9ebbd0d7a974a7e61d050e0bbf67dc3..3855bfd1fb1bdd7c9db129b719ff92138196beda 100644 (file)
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -51,6 +51,7 @@
 #define TIPC_FWD_MSG           1
 #define TIPC_MAX_PORT          0xffffffff
 #define TIPC_MIN_PORT          1
+#define TIPC_ACK_RATE          4       /* ACK at 1/4 of of rcv window size */
 
 enum {
        TIPC_LISTEN = TCP_LISTEN,
@@ -1290,7 +1291,7 @@ static int tipc_wait_for_rcvmsg(struct socket *sock, long *timeop)
 /**
  * tipc_recvmsg - receive packet-oriented message
  * @m: descriptor for message info
- * @buf_len: total size of user buffer area
+ * @buflen: length of user buffer area
  * @flags: receive flags
  *
  * Used for SOCK_DGRAM, SOCK_RDM, and SOCK_SEQPACKET messages.
@@ -1298,89 +1299,79 @@ static int tipc_wait_for_rcvmsg(struct socket *sock, long *timeop)
  *
  * Returns size of returned message data, errno otherwise
  */
-static int tipc_recvmsg(struct socket *sock, struct msghdr *m, size_t buf_len,
-                       int flags)
+static int tipc_recvmsg(struct socket *sock, struct msghdr *m,
+                       size_t buflen,  int flags)
 {
        struct sock *sk = sock->sk;
        struct tipc_sock *tsk = tipc_sk(sk);
-       struct sk_buff *buf;
-       struct tipc_msg *msg;
-       bool is_connectionless = tipc_sk_type_connectionless(sk);
-       long timeo;
-       unsigned int sz;
-       u32 err;
-       int res, hlen;
+       struct sk_buff *skb;
+       struct tipc_msg *hdr;
+       bool connected = !tipc_sk_type_connectionless(sk);
+       int rc, err, hlen, dlen, copy;
+       long timeout;
 
        /* Catch invalid receive requests */
-       if (unlikely(!buf_len))
+       if (unlikely(!buflen))
                return -EINVAL;
 
        lock_sock(sk);
-
-       if (!is_connectionless && unlikely(sk->sk_state == TIPC_OPEN)) {
-               res = -ENOTCONN;
+       if (unlikely(connected && sk->sk_state == TIPC_OPEN)) {
+               rc = -ENOTCONN;
                goto exit;
        }
+       timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
 
-       timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
-restart:
-
-       /* Look for a message in receive queue; wait if necessary */
-       res = tipc_wait_for_rcvmsg(sock, &timeo);
-       if (res)
-               goto exit;
-
-       /* Look at first message in receive queue */
-       buf = skb_peek(&sk->sk_receive_queue);
-       msg = buf_msg(buf);
-       sz = msg_data_sz(msg);
-       hlen = msg_hdr_sz(msg);
-       err = msg_errcode(msg);
-
-       /* Discard an empty non-errored message & try again */
-       if ((!sz) && (!err)) {
+       do {
+               /* Look at first msg in receive queue; wait if necessary */
+               rc = tipc_wait_for_rcvmsg(sock, &timeout);
+               if (unlikely(rc))
+                       goto exit;
+               skb = skb_peek(&sk->sk_receive_queue);
+               hdr = buf_msg(skb);
+               dlen = msg_data_sz(hdr);
+               hlen = msg_hdr_sz(hdr);
+               err = msg_errcode(hdr);
+               if (likely(dlen || err))
+                       break;
                tsk_advance_rx_queue(sk);
-               goto restart;
-       }
+       } while (1);
 
-       /* Capture sender's address (optional) */
-       set_orig_addr(m, msg);
-
-       /* Capture ancillary data (optional) */
-       res = tipc_sk_anc_data_recv(m, msg, tsk);
-       if (res)
+       /* Collect msg meta data, including error code and rejected data */
+       set_orig_addr(m, hdr);
+       rc = tipc_sk_anc_data_recv(m, hdr, tsk);
+       if (unlikely(rc))
                goto exit;
 
-       /* Capture message data (if valid) & compute return value (always) */
-       if (!err) {
-               if (unlikely(buf_len < sz)) {
-                       sz = buf_len;
+       /* Capture data if non-error msg, otherwise just set return value */
+       if (likely(!err)) {
+               copy = min_t(int, dlen, buflen);
+               if (unlikely(copy != dlen))
                        m->msg_flags |= MSG_TRUNC;
-               }
-               res = skb_copy_datagram_msg(buf, hlen, m, sz);
-               if (res)
-                       goto exit;
-               res = sz;
+               rc = skb_copy_datagram_msg(skb, hlen, m, copy);
        } else {
-               if (is_connectionless || err == TIPC_CONN_SHUTDOWN ||
-                   m->msg_control)
-                       res = 0;
-               else
-                       res = -ECONNRESET;
+               copy = 0;
+               rc = 0;
+               if (err != TIPC_CONN_SHUTDOWN && connected && !m->msg_control)
+                       rc = -ECONNRESET;
        }
+       if (unlikely(rc))
+               goto exit;
 
+       /* Caption of data or error code/rejected data was successful */
        if (unlikely(flags & MSG_PEEK))
                goto exit;
 
-       if (likely(!is_connectionless)) {
-               tsk->rcv_unacked += tsk_inc(tsk, hlen + sz);
-               if (unlikely(tsk->rcv_unacked >= (tsk->rcv_win / 4)))
-                       tipc_sk_send_ack(tsk);
-       }
        tsk_advance_rx_queue(sk);
+       if (likely(!connected))
+               goto exit;
+
+       /* Send connection flow control ack when applicable */
+       tsk->rcv_unacked += tsk_inc(tsk, hlen + dlen);
+       if (tsk->rcv_unacked >= tsk->rcv_win / TIPC_ACK_RATE)
+               tipc_sk_send_ack(tsk);
 exit:
        release_sock(sk);
-       return res;
+       return rc ? rc : copy;
 }
 
 /**