doc: slirp supports ICMP echo if enabled in Linux

Since QEMU 0.15, slirp (user mode networking) supports ping to the
Internet, see e6d43cfb1f

Signed-off-by: Gernot Hillier <gernot.hillier@siemens.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
This commit is contained in:
Gernot Hillier 2014-07-10 16:01:25 +02:00 committed by Michael Tokarev
parent b847ae2d60
commit 37cbfcce14

View file

@ -1205,9 +1205,16 @@ 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 GID 100 (usually users group):
@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.