[9front] patch: add listenaddr plan9.ini variable

[covertusername967@gmail.com]

Hello,

This patch changes cpurc to check for a listenaddr= variable set from
plan9.ini.  If set, cpu servers will only listen on the specified
address.


diff -r cc26fdf57bb2 rc/bin/cpurc
--- a/rc/bin/cpurc	Sat Mar 13 14:57:53 2021 +0100
+++ b/rc/bin/cpurc	Sun Mar 14 19:57:16 2021 -0500
@@ -105,11 +105,17 @@
 }){
 	# cpu+auth server
 	auth/keyfs -wp -m /mnt/keys /adm/keys
-	aux/listen -q -t /rc/bin/service.auth -d $serviced tcp
+	if(test -e /env/listenaddr)
+		aux/listen -q -t /rc/bin/service.auth -d $serviced -a $listenaddr tcp
+	if not
+		aux/listen -q -t /rc/bin/service.auth -d $serviced tcp
 }
 if not {
 	# cpu server
-	aux/listen -q -d $serviced tcp
+	if(test -e /env/listenaddr)
+		aux/listen -q -d $serviced -a $listenaddr tcp
+	if not
+		aux/listen -q -d $serviced tcp
 }
 
 if(test -f /dev/apm)
diff -r cc26fdf57bb2 sys/man/8/plan9.ini
--- a/sys/man/8/plan9.ini	Sat Mar 13 14:57:53 2021 +0100
+++ b/sys/man/8/plan9.ini	Sun Mar 14 19:57:16 2021 -0500
@@ -450,6 +450,8 @@
 can be specified with the boot parameter above.
 .SS \fLnora6=
 Disable automatic IPv6 configuration from incoming router advertisements.
+.SS \fLlistenaddr\fI=ip\fP
+On cpu servers, restrict the IP address that listen(8) announces on to the specified address.
 .SS DISKS, TAPES
 (S)ATA controllers are autodetected.
 .SS \fL*nodma=\fP