[Qemu-trivial] [PATCH] doc: slirp supports ICMP echo if enabled in Linux

[Gernot Hillier <gernot.hillier@siemens.com>]

Since QEMU 0.15, slirp (user mode networking) supports ping to the
Internet, see e6d43cfb1f9

Signed-off-by: Gernot Hillier <gernot.hillier@siemens.com>
---
  qemu-doc.texi | 14 +++++++++++---
  1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/qemu-doc.texi b/qemu-doc.texi
index 551619a..fc6e57d 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1205,9 +1205,17 @@ In order to check that the user mode network is 
working, you can ping
  the address 10.0.2.2 and verify that you got an address in the range
  10.0.2.x from the QEMU virtual DHCP server.

-Note that @code{ping} is not supported reliably to the internet as it
-would require root privileges. It means you can only ping the local
-router (10.0.2.2).
+Note that ICMP traffic in general does not work with user mode networking.
+@code{ping}, aka. ICMP echo, to the local router (10.0.2.2) shall work,
+however. If you're using QEMU on Linux >= 3.0, it can use unprivileged ICMP
+ping sockets to allow @code{ping} to the Internet. The host admin has 
to set
+the ping_group_range in order to grant access to those sockets. To 
allow ping
+for the users group (GID 100):
+
+@example
+
+echo 100 100 > /proc/sys/net/ipv4/ping_group_range
+@end example

  When using the built-in TFTP server, the router is also the TFTP
  server.
-- 
1.8.4