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aux/trampoline: Implement inactivity timeout (-t option)

Using aux/trampoline to relay udp traffic needs a inactivity
timeout to be practical as there is no explicit connection
termination.

--- a/sys/man/8/trampoline

+++ b/sys/man/8/trampoline

@@ -13,6 +13,9 @@

 [

 .B -m

 .I netdir

+] [

+.B -t

+.I timeout

 ]

 .I addr

 .SH DESCRIPTION

@@ -55,6 +58,11 @@

 and the attribute

 .BR trampok .

 If no such entry is found, the call is rejected.

+.TP

+.BI -t " timeout

+Terminates the connection after

+.I timeout

+milliseconds of inactivity.

 .PD

 .SH FILES

 .TF /sys/log/trampoline

--- a/sys/src/cmd/aux/trampoline.c

+++ b/sys/src/cmd/aux/trampoline.c

@@ -22,14 +22,16 @@

 void		xfer(int, int);

 void		xfer9p(int, int);

 Endpoints*	getendpoints(char*);

-void		freeendpoints(Endpoints*);

 char*		iptomac(char*, char*);

 int		macok(char*);

+int		timeout;

+int		activity;

+

 void

 usage(void)

 {

-	fprint(2, "usage: trampoline [-9] [-a addr] [-m netdir] addr\n");

+	fprint(2, "usage: trampoline [-9] [-a addr] [-m netdir] [-t timeout] addr\n");

 	exits("usage");

 }

@@ -54,6 +56,9 @@

 	case 'm':

 		checkmac = EARGF(usage());

 		break;

+	case 't':

+		timeout = atoi(EARGF(usage()));

+		break;

 	default:

 		usage();

 	}ARGEND;

@@ -71,6 +76,9 @@

 		}

 	}

+	if(timeout > 0)

+		alarm(timeout);

+

 	fd0 = 0;

 	fd1 = 1;

 	if(altaddr){

@@ -84,10 +92,28 @@

 		sysfatal("dial %s: %r", argv[0]);

 	rfork(RFNOTEG);

-	switch(fork()){

+	if(timeout > 0){

+		alarm(0);

+		switch(rfork(RFPROC|RFMEM)){

+		case -1:

+			fprint(2, "%s: fork: %r\n", argv0);

+			exits("fork");

+		case 0:

+			break;

+		default:

+			do {

+				activity = 0;

+				sleep(timeout);

+			} while(activity);

+			postnote(PNGROUP, getpid(), "timeout");

+			exits("timeout");

+		}

+	}

+	switch(rfork(RFPROC|RFMEM)){

 	case -1:

 		fprint(2, "%s: fork: %r\n", argv0);

-		exits("dial");

+		if(timeout <= 0) exits("fork");

+		break;

 	case 0:

 		(*x)(fd0, fd);

 		break;

@@ -95,8 +121,8 @@

 		(*x)(fd, fd1);

 		break;

 	}

-	postnote(PNGROUP, getpid(), "die yankee pig dog");

-	exits(0);

+	postnote(PNGROUP, getpid(), "hangup");

+	exits(nil);

 }

 void

@@ -105,9 +131,12 @@

 	char buf[12*1024];

 	int n;

-	while((n = read(from, buf, sizeof buf)) > 0)

+	while((n = read(from, buf, sizeof buf)) > 0){

 		if(write(to, buf, n) < 0)

 			break;

+		if(timeout > 0)

+			activity = 1;

+	}

 }

 void

@@ -134,10 +163,10 @@

 		}

 		if(readn(from, buf+4, n-4) != n-4)

 			break;

-		if(write(to, buf, n) != n){

-			sysfatal("oops: %r");

+		if(write(to, buf, n) != n)

 			break;

-		}

+		if(timeout > 0)

+			activity = 1;

 	}

 }

@@ -192,16 +221,6 @@

 	return ep;

 }

-void

-freeendpoints(Endpoints *ep)

-{

-	free(ep->lsys);

-	free(ep->rsys);

-	free(ep->lserv);

-	free(ep->rserv);

-	free(ep);

-}

-

 char*

 iptomac(char *ip, char *net)

 {

@@ -237,5 +256,5 @@

 	if(mac == nil)

 		return 0;

 	free(p = csgetvalue("/net", "ether", mac, "trampok", nil));

-	return !(p == nil);

+	return p != nil;

 }