slirp: Forward ICMP echo requests via unprivileged socketsv0.15.0-rc0

Linux 3.0 gained support for unprivileged ICMP ping sockets. Use this
feature to forward guest pings to the outer world. 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):

echo 100 100 > /proc/sys/net/ipv4/ping_group_range

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 35 insertions, 0 deletions

diff --git a/slirp.c b/slirp.c
index 549ee1d..55f35a1 100644
--- a/slirp.c
+++ b/slirp.c
@@ -376,6 +376,30 @@ void slirp_select_fill(int *pnfds, fd_set *readfds, fd_set *writefds,
                 UPD_NFDS(so->s);
             }
         }
+
+        /*
+         * ICMP sockets
+         */
+        for (so = slirp->icmp.so_next; so != &slirp->icmp; so = so_next) {
+            so_next = so->so_next;
+
+            /*
+             * See if it's timed out
+             */
+            if (so->so_expire) {
+                if (so->so_expire <= curtime) {
+                    icmp_detach(so);
+                    continue;
+                } else {
+                    do_slowtimo = 1; /* Let socket expire */
+                }
+            }
+
+            if (so->so_state & SS_ISFCONNECTED) {
+                FD_SET(so->s, readfds);
+                UPD_NFDS(so->s);
+            }
+        }
     }
 
     *pnfds = nfds;
@@ -542,6 +566,17 @@ void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
                     sorecvfrom(so);
                 }
             }
+
+            /*
+             * Check incoming ICMP relies.
+             */
+            for (so = slirp->icmp.so_next; so != &slirp->icmp; so = so_next) {
+                so_next = so->so_next;
+
+                if (so->s != -1 && FD_ISSET(so->s, readfds)) {
+                    icmp_receive(so);
+                }
+            }
         }
 
         /*