From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Mon, 29 Sep 2014 14:17:13 +0000 (+0100)
Subject: polypath: Provide Linux interface monitor
X-Git-Tag: proposed.polypath.v4~19
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=secnet.git;a=commitdiff_plain;h=ed5d1eea357995d2c1e38b4ef3fffc7ebc891d8d

polypath: Provide Linux interface monitor

This script monitors the local network interfaces and prints output as
interfaces and addresses appear and disappear.

Install it in $(datarootdir).  Provide $(datarootdir) to C code via a
-D compiler flag.  Provide the appropriate path as the default setting
for `monitor-command' in the polypath module.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---

diff --git a/Makefile.in b/Makefile.in
index 841a49b..f68022a 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -30,11 +30,13 @@ RM:=@RM@
 CC:=@CC@
 INSTALL:=@INSTALL@
 INSTALL_PROGRAM:=@INSTALL_PROGRAM@
+INSTALL_SCRIPT:=@INSTALL_SCRIPT@
 
 prefix:=@prefix@
 exec_prefix:=@exec_prefix@
 sbindir:=@sbindir@
 sysconfdir:=@sysconfdir@
+datarootdir:=@datarootdir@
 transform:=@program_transform_name@
 mandir:=@mandir@
 
@@ -47,7 +49,7 @@ CFLAGS:=-Wall @WRITESTRINGS@ @CFLAGS@ -Werror \
 	-Wno-strict-aliasing -fno-strict-aliasing \
 	-MMD
 ALL_CFLAGS:=@DEFS@ -I$(srcdir) -I. $(CFLAGS) $(EXTRA_CFLAGS)
-CPPFLAGS:=@CPPFLAGS@ $(EXTRA_CPPFLAGS)
+CPPFLAGS:=@CPPFLAGS@ -DDATAROOTDIR='"$(datarootdir)"' $(EXTRA_CPPFLAGS)
 LDFLAGS:=@LDFLAGS@ $(EXTRA_LDFLAGS)
 LDLIBS:=@LIBS@ $(EXTRA_LDLIBS)
 
@@ -166,6 +168,7 @@ check-ipaddrset: ipaddrset-test.py ipaddrset.py ipaddrset-test.expected
 installdirs:
 	$(INSTALL) -d $(prefix)/share/secnet $(sbindir)
 	$(INSTALL) -d $(mandir)/man8
+	$(INSTALL) -d $(datarootdir)/secnet
 
 install: installdirs
 	set -e; ok=true; for f in $(STALE_PYTHON_FILES); do \
@@ -179,6 +182,8 @@ install: installdirs
 	$(INSTALL_PROGRAM) secnet $(sbindir)/`echo secnet|sed '$(transform)'`
 	$(INSTALL_PROGRAM) ${srcdir}/make-secnet-sites $(sbindir)/`echo make-secnet-sites|sed '$(transform)'`
 	$(INSTALL) ${srcdir}/ipaddrset.py $(prefix)/share/secnet/ipaddrset.py
+	$(INSTALL_SCRIPT) ${srcdir}/polypath-interface-monitor-linux \
+		$(datarootdir)/secnet/.
 	$(INSTALL) secnet.8 $(mandir)/man8/secnet.8
 
 install-force:
diff --git a/polypath-interface-monitor-linux b/polypath-interface-monitor-linux
new file mode 100755
index 0000000..1b02bfa
--- /dev/null
+++ b/polypath-interface-monitor-linux
@@ -0,0 +1,82 @@
+#!/usr/bin/perl -w
+use strict;
+use IO::Handle;
+
+my $us = $0;
+$us =~ s{.*/}{};
+
+die "$us: no arguments permitted\n" if @ARGV;
+
+our ($monh,$monchild);
+
+our %reported;
+#  no entry: not reported, does not exist
+#  /ry+/: reported, entry exists
+# during processing only:
+#  /r/: reported, may not still exist
+#  /y+/: not reported, entry exists
+
+sub killmonitor () {
+    return unless $monchild;
+    kill 9, $monchild
+	or warn "$us: cannot kill monitor child [$monchild]: $!\n";
+    $monchild=undef;
+    close $monh;
+}
+
+END { killmonitor(); }
+
+my $restart;
+
+for (;;) {
+    my $o;
+    eval {
+	if (!$monh) {
+	    killmonitor();
+	    $monh = new IO::File;
+	    $monchild = open $monh, "-|", qw(ip -o monitor addr)
+		or die "spawn monitor: $!\n";
+	    sleep(1) if $restart++;
+	} else {
+	    my $discard;
+	    my $got = sysread $monh, $discard, 4096;
+	    die "read monitor: $!\n" unless defined $got;
+	    die "monitor failed\n" unless $got;
+	}
+	$_='r' foreach values %reported;
+	foreach my $ip (qw(4 6)) {
+	    my $addrh = new IO::File;
+	    open $addrh, "-|", qw(ip -o), "-$ip", qw(addr show)
+		or die "spawn addr $ip show: $!\n";
+	    my $afstr = $ip==4 ? 'inet' : $ip==6 ? 'inet6' : die;
+	    while (<$addrh>) {
+		if (m{^\d+\:\s*(\S+)\s+$afstr\s+([0-9a-z.:]+)(?:/\d+)?\s}) {
+		    my $outline = "$ip $1 $2";
+		    $reported{$outline} .= "y";
+		} else {
+		    chomp;
+		    warn "unexpected output from addr $ip show: $_\n";
+		}
+	    }
+	    my $r = close $addrh;
+	    die "addr $ip show failed $!\n" unless $r;
+	    $o = '';
+	}
+	foreach my $k (keys %reported) {
+	    local $_ = $reported{$k};
+	    if (m/^r$/) {
+		$o .= "-$k\n";
+		delete $reported{$k};
+	    } elsif (m/^y/) {
+		$o .= "+$k\n";
+	    }
+	}
+    };
+    if ($@) {
+	print STDERR "$us: $@";
+	sleep 5;
+	next;
+    }
+    print $o or die $!;
+    STDOUT->flush or die $!;
+}
diff --git a/polypath.c b/polypath.c
index 27c3f46..3bd835e 100644
--- a/polypath.c
+++ b/polypath.c
@@ -43,7 +43,11 @@ static const char *const default_ifname_pats[] = {
 };
 
 static const char *const default_monitor_command[] = {
+#if __linux__
+    DATAROOTDIR "/secnet/" "polypath-interface-monitor-linux", 0
+#else
     0
+#endif
 };
 
 static const char *polypath_addr_to_string(void *commst,