[PATCH 1/3] Revert "fwd: Update all port maps before applying exclusions"

[David Gibson <david@gibson.dropbear.id.au>]

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>
---
 fwd.c | 47 +++++++++++++++++++++++------------------------
 1 file changed, 23 insertions(+), 24 deletions(-)

diff --git a/fwd.c b/fwd.c
index 68bb1166..7b6c40fb 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);
 }
 
 /**
-- 
2.51.1