Prevent UA frame from terminating socket w/o DISC

Changes:

    * Add a "pending disconnect" state to enum patty_ax25_sock_state
     (PATTY_AX25_SOCK_PENDING_DISCONNECT), used when an originating
     system sends a DISC frame, pending a UA response

    * When handling a UA frame, rather than terminating a socket in the
      established state implicitly, check for a "pending disconnect"
      state explicitly

Other changes:

    * When a remote socket has already been obtained in handle_frame()
      in src/server.c, pass that socket to any other method that would
      otherwise be looking up the same socket

include/patty/ax25/sock.h

@@ -30,6 +30,7 @@ enum patty_ax25_sock_status {
     PATTY_AX25_SOCK_LISTENING,
     PATTY_AX25_SOCK_PENDING_ACCEPT,
     PATTY_AX25_SOCK_PENDING_CONNECT,
+    PATTY_AX25_SOCK_PENDING_DISCONNECT,
     PATTY_AX25_SOCK_ESTABLISHED,
     PATTY_AX25_SOCK_PROMISC
 };

src/server.c

@@ -292,8 +292,13 @@ static int sock_shutdown(patty_ax25_server *server,
                          patty_ax25_sock *sock) {
     fd_clear(server, sock->fd);
 
-    return sock->status == PATTY_AX25_SOCK_ESTABLISHED?
+    if (sock->status != PATTY_AX25_SOCK_ESTABLISHED) {
-        patty_ax25_sock_send_disc(sock, PATTY_AX25_FRAME_POLL): 0;
+        return 0;
+    }
+
+    sock->status = PATTY_AX25_SOCK_PENDING_DISCONNECT;
+
+    return patty_ax25_sock_send_disc(sock, PATTY_AX25_FRAME_POLL);
 }
 
 static int sock_save(patty_ax25_server *server,
@@ -318,6 +323,7 @@ static int sock_save(patty_ax25_server *server,
 
             break;
 
+        case PATTY_AX25_SOCK_PENDING_DISCONNECT:
         case PATTY_AX25_SOCK_CLOSED:
         case PATTY_AX25_SOCK_PROMISC:
             break;
@@ -360,6 +366,7 @@ static int sock_close(patty_ax25_server *server,
 
         case PATTY_AX25_SOCK_PENDING_ACCEPT:
         case PATTY_AX25_SOCK_PENDING_CONNECT:
+        case PATTY_AX25_SOCK_PENDING_DISCONNECT:
         case PATTY_AX25_SOCK_ESTABLISHED:
             if (sock_delete_remote(server, sock) < 0) {
                 goto error_sock_delete_remote;
@@ -1130,12 +1137,9 @@ static int reply_ua(patty_ax25_if *iface,
 
 static int handle_frmr(patty_ax25_server *server,
                        patty_ax25_if *iface,
+                       patty_ax25_sock *sock,
                        patty_ax25_frame *frame) {
-    patty_ax25_sock *sock;
+    if (sock == NULL) {
-
-    if ((sock = sock_by_addrpair(server->socks_remote,
-                                 &frame->dest,
-                                 &frame->src)) == NULL) {
         return 0;
     }
 
@@ -1216,14 +1220,12 @@ error_client_by_sock:
 
 static int handle_ua(patty_ax25_server *server,
                      patty_ax25_if *iface,
+                     patty_ax25_sock *sock,
                      patty_ax25_frame *frame) {
     int client;
-    patty_ax25_sock *sock;
     patty_ax25_call_connect_response response;
 
-    if ((sock = sock_by_addrpair(server->socks_remote,
+    if (sock == NULL) {
-                                 &frame->dest,
-                                 &frame->src)) == NULL) {
         return reply_dm(iface, frame, PATTY_AX25_FRAME_FINAL);
     }
 
@@ -1231,9 +1233,12 @@ static int handle_ua(patty_ax25_server *server,
         case PATTY_AX25_SOCK_PENDING_CONNECT:
             break;
 
-        case PATTY_AX25_SOCK_ESTABLISHED:
+        case PATTY_AX25_SOCK_PENDING_DISCONNECT:
             return sock_close(server, sock);
 
+        case PATTY_AX25_SOCK_ESTABLISHED:
+            return 0;
+
         default:
             return reply_dm(iface, frame, PATTY_AX25_FRAME_FINAL);
     }
@@ -1269,18 +1274,12 @@ error_client_by_sock:
 
 static int handle_dm(patty_ax25_server *server,
                      patty_ax25_if *iface,
+                     patty_ax25_sock *sock,
                      patty_ax25_frame *frame) {
     int client;
-    patty_ax25_sock *sock;
     patty_ax25_call_connect_response response;
 
-    if ((sock = sock_by_addrpair(server->socks_remote,
+    if (sock == NULL || sock->status != PATTY_AX25_SOCK_PENDING_CONNECT) {
-                                 &frame->dest,
-                                 &frame->src)) == NULL) {
-        return 0;
-    }
-
-    if (sock->status != PATTY_AX25_SOCK_PENDING_CONNECT) {
         return 0;
     }
 
@@ -1332,22 +1331,27 @@ error_write:
 
 static int handle_disc(patty_ax25_server *server,
                        patty_ax25_if *iface,
+                       patty_ax25_sock *sock,
                        patty_ax25_frame *frame) {
-    patty_ax25_sock *sock;
+    if (sock == NULL) {
-
+        goto reply_dm;
-    if ((sock = sock_by_addrpair(server->socks_remote,
-                                 &frame->dest,
-                                 &frame->src)) == NULL) {
-        return 0;
-    }
-
-    if (sock->status != PATTY_AX25_SOCK_ESTABLISHED) {
-        return frame->pf? reply_dm(iface, frame, PATTY_AX25_FRAME_FINAL): 0;
     }
 
+    switch (sock->status) {
+        case PATTY_AX25_SOCK_ESTABLISHED:
             (void)sock_close(server, sock);
 
             return reply_ua(iface, frame, PATTY_AX25_FRAME_FINAL);
+
+        case PATTY_AX25_SOCK_PENDING_DISCONNECT:
+            return 0;
+
+        default:
+            break;
+    }
+
+reply_dm:
+    return reply_dm(iface, frame, PATTY_AX25_FRAME_FINAL);
 }
 
 static int handle_rej(patty_ax25_server *server,
@@ -1355,6 +1359,10 @@ static int handle_rej(patty_ax25_server *server,
                       patty_ax25_frame *frame) {
     unsigned int i;
 
+    if (sock == NULL) {
+        return 0;
+    }
+
     for (i=frame->nr; i<sock->seq_send; i++) {
         if (patty_ax25_sock_resend(sock, i) < 0) {
             goto error_sock_resend;
@@ -1370,6 +1378,10 @@ error_sock_resend:
 static int handle_srej(patty_ax25_server *server,
                        patty_ax25_sock *sock,
                        patty_ax25_frame *frame) {
+    if (sock == NULL) {
+        return 0;
+    }
+
     /*
      * TODO: Read the fine print of section 4.3.2.4
      */
@@ -1525,16 +1537,16 @@ static int handle_frame(patty_ax25_server *server,
     }
 
     switch (frame.type) {
-        case PATTY_AX25_FRAME_UA:    return handle_ua(server, iface, &frame);
-        case PATTY_AX25_FRAME_DM:    return handle_dm(server, iface, &frame);
-        case PATTY_AX25_FRAME_SABM:
-        case PATTY_AX25_FRAME_SABME: return handle_sabm(server, iface, &frame);
-        case PATTY_AX25_FRAME_DISC:  return handle_disc(server, iface, &frame);
         case PATTY_AX25_FRAME_I:     return handle_i(server, iface, sock, &frame);
         case PATTY_AX25_FRAME_REJ:   return handle_rej(server, sock, &frame);
         case PATTY_AX25_FRAME_SREJ:  return handle_srej(server, sock, &frame);
         case PATTY_AX25_FRAME_XID:   return handle_xid(server, iface, &frame, buf, offset, len);
-        case PATTY_AX25_FRAME_FRMR:  return handle_frmr(server, iface, &frame);
+        case PATTY_AX25_FRAME_SABM:
+        case PATTY_AX25_FRAME_SABME: return handle_sabm(server, iface, &frame);
+        case PATTY_AX25_FRAME_UA:    return handle_ua(server, iface, sock, &frame);
+        case PATTY_AX25_FRAME_DM:    return handle_dm(server, iface, sock, &frame);
+        case PATTY_AX25_FRAME_DISC:  return handle_disc(server, iface, sock, &frame);
+        case PATTY_AX25_FRAME_FRMR:  return handle_frmr(server, iface, sock, &frame);
 
         default:
             break;