code: plan9front

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ip/ppp: fix race condition with rfork()

ipinprocpid is static so shared with parent and child,
so we need a temporary variable on the local stack
to properly assign ipinprocpid.

--- a/sys/src/cmd/ip/ppp/ppp.c

+++ b/sys/src/cmd/ip/ppp/ppp.c

@@ -1640,7 +1640,7 @@

 ipopen(PPP *ppp)

 {

 	static int ipinprocpid;

-	int n, cfd, fd;

+	int n, cfd, fd, pid;

 	char path[128];

 	char buf[128];

@@ -1676,7 +1676,7 @@

 		close(cfd);

 		ppp->ipfd = fd;

-		switch(ipinprocpid = rfork(RFPROC|RFMEM|RFNOWAIT)){

+		switch(pid = rfork(RFPROC|RFMEM|RFNOWAIT)){

 		case -1:

 			terminate(ppp, "forking ipinproc", 1);

 		case 0:

@@ -1684,6 +1684,7 @@

 			terminate(ppp, "ipinproc", 0);

 			exits(nil);

 		}

+		ipinprocpid = pid;

 		if(validv4(ppp->local)){

 			if(!validv4(ppp->remote))