Cleanup in src/server.c, handle_sock()

Changes:

    * Implement handle_sock_dgram() to specifically handle datagram
      (UI frame-only) sockets; this fixes issues wherein logic
      specific to SOCK_STREAM timers would be erroneously applied
      to datagram sockets

    * Always tick Timers T1, T2 and T3

    * Some slight code reorganization for improved readability of
      control flow

src/server.c

@@ -1805,6 +1805,35 @@ error_io:
     return -1;
 }
 
+static int handle_sock_dgram(patty_ax25_server *server,
+                             patty_ax25_sock *sock) {
+    ssize_t len;
+
+    if (!FD_ISSET(sock->fd, &server->fds_r)) {
+        return 0;
+    }
+
+    if ((len = read(sock->fd, sock->rx_buf, sock->n_maxlen_rx)) < 0) {
+        if (errno == EIO) {
+            (void)sock_close(server, sock);
+        } else {
+            goto error_unknown;
+        }
+    } else if (len == 0) {
+        (void)sock_close(server, sock);
+    } else if (len > 0) {
+        if (patty_ax25_sock_write(sock, sock->rx_buf, len) < 0) {
+            goto error_sock_write;
+        }
+    }
+
+    return 0;
+
+error_sock_write:
+error_unknown:
+    return -1;
+}
+
 static int handle_sock_raw(patty_ax25_server *server,
                            patty_ax25_sock *sock) {
     if (!FD_ISSET(sock->fd, &server->fds_r) || sock->iface == NULL) {
@@ -1839,14 +1868,23 @@ static int handle_sock(uint32_t key,
 
     ssize_t len;
 
-    if (sock->type == PATTY_AX25_SOCK_RAW) {
+    switch (sock->type) {
-        return handle_sock_raw(server, sock);
+        case PATTY_AX25_SOCK_DGRAM:
+            return handle_sock_dgram(server, sock);
+
+        case PATTY_AX25_SOCK_RAW:
+            return handle_sock_raw(server, sock);
+
+        case PATTY_AX25_SOCK_STREAM:
+            break;
     }
 
+    patty_timer_tick(&sock->timer_t1, &server->elapsed);
+    patty_timer_tick(&sock->timer_t2, &server->elapsed);
+    patty_timer_tick(&sock->timer_t3, &server->elapsed);
+
     switch (sock->state) {
         case PATTY_AX25_SOCK_PENDING_CONNECT:
-            patty_timer_tick(&sock->timer_t1, &server->elapsed);
-
             if (patty_timer_expired(&sock->timer_t1)) {
                 if (sock->retries) {
                     int ret = patty_ax25_sock_send_sabm(sock, PATTY_AX25_FRAME_POLL);
@@ -1869,12 +1907,9 @@ static int handle_sock(uint32_t key,
                 }
             }
 
-            goto done;
+            return 0;
 
         case PATTY_AX25_SOCK_ESTABLISHED:
-            patty_timer_tick(&sock->timer_t2, &server->elapsed);
-            patty_timer_tick(&sock->timer_t3, &server->elapsed);
-
             if (patty_timer_expired(&sock->timer_t1)) {
                 if (sock->retries) {
                     int ret = patty_ax25_sock_send_rr(sock,
@@ -1921,7 +1956,7 @@ static int handle_sock(uint32_t key,
     }
 
     if (!FD_ISSET(sock->fd, &server->fds_r)) {
-        goto done;
+        return 0;
     }
 
     /*
@@ -1945,32 +1980,27 @@ static int handle_sock(uint32_t key,
     if ((len = read(sock->fd, sock->rx_buf, sock->n_maxlen_rx)) < 0) {
         if (errno == EIO) {
             (void)sock_shutdown(server, sock);
-
+        } else {
-            goto done;
+            goto error_unknown;
         }
-
-        goto error_io;
     } else if (len == 0) {
         (void)sock_shutdown(server, sock);
+    } else if (len > 0) {
+        if (patty_ax25_sock_write(sock, sock->rx_buf, len) < 0) {
+            goto error_sock_write;
+        }
 
-        goto done;
+        /*
+         * AX.25 v2.2, Section 6.4.1, "Sending I Frames"
+         */
+        patty_timer_start(&sock->timer_t1, sock->n_ack);
     }
 
-    if (patty_ax25_sock_write(sock, sock->rx_buf, len) < 0) {
-        goto error_sock_write;
-    }
-
-    /*
-     * AX.25 v2.2, Section 6.4.1, "Sending I Frames"
-     */
-    patty_timer_start(&sock->timer_t1, sock->n_ack);
-
-done:
     return 0;
 
 error_client_by_sock:
 error_sock_write:
-error_io:
+error_unknown:
     return -1;
 }