ftp: Do not base seq on number of pending commands

Previously, seq was computed as the result of |pending_commands|+1. This
opened the possibility to override queued commands, as well as logging
the same pending ftp reply multiple times.

For example, when commands 1, 2, 3 are pending, command 1 may be dequeued,
but the incoming command then receives seq 3 and overrides the already
pending command 3. The second scenario happens when ftp_reply() selected
command 3 as pending for logging, but is then followed by many ftp_request()
events. This resulted in command 3's response being logged for every
following ftp_request() over and over again.

Avoid both scenarios by tracking the command sequence as an absolute counter.

scripts/base/protocols/ftp/info.zeek

@@ -64,6 +64,9 @@ export {
 		## to are tracked here.
 		pending_commands:   PendingCmds;
 
+		## Sequence number of previous command.
+		command_seq:        count &default=0;
+
 		## Indicates if the session is in active or passive mode.
 		passive:            bool &default=F;
 

scripts/base/protocols/ftp/main.zeek

@@ -165,7 +165,7 @@ function set_ftp_session(c: connection)
 		Conn::register_removal_hook(c, finalize_ftp);
 
 		# Add a shim command so the server can respond with some init response.
-		add_pending_cmd(c$ftp$pending_commands, "<init>", "");
+		add_pending_cmd(c$ftp$pending_commands, ++c$ftp$command_seq, "<init>", "");
 		}
 	}
 
@@ -270,7 +270,7 @@ event ftp_request(c: connection, command: string, arg: string) &priority=5
 
 	# Queue up the new command and argument
 	if ( |c$ftp$pending_commands| < max_pending_commands )
-		add_pending_cmd(c$ftp$pending_commands, command, arg);
+		add_pending_cmd(c$ftp$pending_commands, ++c$ftp$command_seq, command, arg);
 	else
 		Reporter::conn_weird("FTP_too_many_pending_commands", c,
 				     cat(|c$ftp$pending_commands|), "FTP");

scripts/base/protocols/ftp/utils-commands.zeek

@@ -78,9 +78,9 @@ export {
 	};
 }
 
-function add_pending_cmd(pc: PendingCmds, cmd: string, arg: string): CmdArg
+function add_pending_cmd(pc: PendingCmds, seq: count, cmd: string, arg: string): CmdArg
 	{
-	local ca = [$cmd = cmd, $arg = arg, $seq=|pc|+1, $ts=network_time()];
+	local ca = [$cmd = cmd, $arg = arg, $seq=seq, $ts=network_time()];
 	pc[ca$seq] = ca;
 
 	return ca;

testing/external/commit-hash.zeek-testing

@@ -1 +1 @@
-f0dfda82f616d478df1a290116b4b7efdd82f00a
+9e2b8aaa316d6b818fa32c730fcc90ca8b401b68

testing/external/commit-hash.zeek-testing-private

@@ -1 +1 @@
-eea2f9972f5b103048a40d07b3f14c41d92336bc
+0e810e51b5fdeacfab53b5655023190c84f86f2e