init.rc: allow IPPROTO_ICMP support

Allow userspace programs to create IPPROTO_ICMP sockets.

This socket type allows an unprivileged program to safely
send ICMP_ECHO messages and receive the corresponding
ICMP_ECHOREPLY messages, without relying on raw sockets or
setuid programs.

Please see http://lwn.net/Articles/443051/ for details.

In particular, this allows us to use a version of ping
which doesn't have any capabilities
(https://android-review.googlesource.com/52072).
In addition, this allows us to safely implement an IPv4 ICMP
based version of InetAddress.isReachable()
(https://code.google.com/p/android/issues/detail?id=20106)

Change-Id: I876718151efa8219c4f34f573e35e21256fe2316
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 871a1f7..d6182e8 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -92,6 +92,7 @@
     write /proc/sys/kernel/kptr_restrict 2
     write /proc/sys/kernel/dmesg_restrict 1
     write /proc/sys/vm/mmap_min_addr 32768
+    write /proc/sys/net/ipv4/ping_group_range "0 2147483647"
     write /proc/sys/kernel/sched_rt_runtime_us 950000
     write /proc/sys/kernel/sched_rt_period_us 1000000