Revert "fwd: Update all port maps before applying exclusions"

This reverts commit 81942a2417357ff10b02ccc8275cde2d4d6fbfbe.

That commit was based on the premise of trying to make all the exclusions
use the "latest" scan data.  That was a fundamentally wrong approach: what
we need to exclude is listening ports that pasta itself has created.  That
is, we need to exclude ports that we were _already_ listening on, not ones
that we intend to listen once we rebind - we *want* the old data.

Reverting this reduces the cases in which bug 176 occurs, but it's not a
complete fix.

Link: https://bugs.passt.top/show_bug.cgi?id=176
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 23 insertions, 24 deletions

diff --git a/fwd.c b/fwd.c
index 68bb116..7b6c40f 100644
--- a/fwd.c
+++ b/fwd.c
@@ -358,8 +358,10 @@ static void procfs_scan_listen(int fd, unsigned int lstate, uint8_t *map)
 /**
  * fwd_scan_ports_tcp() - Scan /proc to update TCP forwarding map
  * @fwd:	Forwarding information to update
+ * @rev:	Forwarding information for the reverse direction
  */
-static void fwd_scan_ports_tcp(struct fwd_ports *fwd)
+static void fwd_scan_ports_tcp(struct fwd_ports *fwd,
+			       const struct fwd_ports *rev)
 {
 	if (fwd->mode != FWD_AUTO)
 		return;
@@ -367,15 +369,20 @@ static void fwd_scan_ports_tcp(struct fwd_ports *fwd)
 	memset(fwd->map, 0, PORT_BITMAP_SIZE);
 	procfs_scan_listen(fwd->scan4, TCP_LISTEN, fwd->map);
 	procfs_scan_listen(fwd->scan6, TCP_LISTEN, fwd->map);
+	bitmap_and_not(fwd->map, PORT_BITMAP_SIZE, fwd->map, rev->map);
 }
 
 /**
  * fwd_scan_ports_udp() - Scan /proc to update UDP forwarding map
  * @fwd:	Forwarding information to update
+ * @rev:	Forwarding information for the reverse direction
  * @tcp_fwd:	Corresponding TCP forwarding information
+ * @tcp_rev:	TCP forwarding information for the reverse direction
  */
 static void fwd_scan_ports_udp(struct fwd_ports *fwd,
-			       const struct fwd_ports *tcp_fwd)
+			       const struct fwd_ports *rev,
+			       const struct fwd_ports *tcp_fwd,
+			       const struct fwd_ports *tcp_rev)
 {
 	if (fwd->mode != FWD_AUTO)
 		return;
@@ -391,6 +398,14 @@ static void fwd_scan_ports_udp(struct fwd_ports *fwd,
 	 */
 	procfs_scan_listen(tcp_fwd->scan4, TCP_LISTEN, fwd->map);
 	procfs_scan_listen(tcp_fwd->scan6, TCP_LISTEN, fwd->map);
+
+	/* This means we need to skip numbers of TCP ports bound on the other
+	 * side, too. Otherwise, we would detect corresponding UDP ports as
+	 * bound and try to forward them from the opposite side, but it's
+	 * already us handling them.
+	 */
+	bitmap_and_not(fwd->map, PORT_BITMAP_SIZE, fwd->map, rev->map);
+	bitmap_and_not(fwd->map, PORT_BITMAP_SIZE, fwd->map, tcp_rev->map);
 }
 
 /**
@@ -399,28 +414,12 @@ static void fwd_scan_ports_udp(struct fwd_ports *fwd,
  */
 static void fwd_scan_ports(struct ctx *c)
 {
-	fwd_scan_ports_tcp(&c->tcp.fwd_out);
-	fwd_scan_ports_tcp(&c->tcp.fwd_in);
-	fwd_scan_ports_udp(&c->udp.fwd_out, &c->tcp.fwd_out);
-	fwd_scan_ports_udp(&c->udp.fwd_in, &c->tcp.fwd_in);
-
-	if (c->tcp.fwd_out.mode == FWD_AUTO) {
-		bitmap_and_not(c->tcp.fwd_out.map, PORT_BITMAP_SIZE,
-			       c->tcp.fwd_out.map, c->tcp.fwd_in.map);
-	}
-	if (c->tcp.fwd_in.mode == FWD_AUTO) {
-		bitmap_and_not(c->tcp.fwd_in.map, PORT_BITMAP_SIZE,
-			       c->tcp.fwd_in.map, c->tcp.fwd_out.map);
-	}
-
-	if (c->udp.fwd_out.mode == FWD_AUTO) {
-		bitmap_and_not(c->udp.fwd_out.map, PORT_BITMAP_SIZE,
-			       c->udp.fwd_out.map, c->udp.fwd_in.map);
-	}
-	if (c->udp.fwd_in.mode == FWD_AUTO) {
-		bitmap_and_not(c->udp.fwd_in.map, PORT_BITMAP_SIZE,
-			       c->udp.fwd_in.map, c->udp.fwd_out.map);
-	}
+	fwd_scan_ports_tcp(&c->tcp.fwd_out, &c->tcp.fwd_in);
+	fwd_scan_ports_tcp(&c->tcp.fwd_in, &c->tcp.fwd_out);
+	fwd_scan_ports_udp(&c->udp.fwd_out, &c->udp.fwd_in,
+			   &c->tcp.fwd_out, &c->tcp.fwd_in);
+	fwd_scan_ports_udp(&c->udp.fwd_in, &c->udp.fwd_out,
+			   &c->tcp.fwd_in, &c->tcp.fwd_out);
 }
 
 /**