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>

1 files changed, 50 insertions, 59 deletions

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 8a4e9fe5f9eb..3855bfd1fb1b 100644
--- 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;
 }
 
 /**