slirp: Adding IPv6, ICMPv6 Echo and NDP autoconfiguration

This patch adds the functions needed to handle IPv6 packets. ICMPv6 and
NDP headers are implemented.

Slirp is now able to send NDP Router or Neighbor Advertisement when it
receives Router or Neighbor Solicitation. Using a 64bit-sized IPv6
prefix, the guest is now able to perform stateless autoconfiguration
(SLAAC) and to compute its IPv6 address.

This patch adds an ndp_table, mainly inspired by arp_table, to keep an
NDP cache and manage network address resolution.
Slirp regularly sends NDP Neighbor Advertisement, as recommended by the
RFC, to make the guest refresh its route.

This also adds ip6_cksum() to compute ICMPv6 checksums using IPv6
pseudo-header.

Some #define ETH_* are moved upper in slirp.h to make them accessible to
other slirp/*.h

Signed-off-by: Guillaume Subiron <maethor@subiron.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>

1 files changed, 58 insertions, 3 deletions

diff --git a/slirp/slirp.c b/slirp/slirp.c
index 0466d330da..049c2cfb1e 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -210,10 +210,12 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
 
     slirp_init_once();
 
+    slirp->grand = g_rand_new();
     slirp->restricted = restricted;
 
     if_init(slirp);
     ip_init(slirp);
+    ip6_init(slirp);
 
     /* Initialise mbufs *after* setting the MTU */
     m_init(slirp);
@@ -221,6 +223,19 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
     slirp->vnetwork_addr = vnetwork;
     slirp->vnetwork_mask = vnetmask;
     slirp->vhost_addr = vhost;
+#if defined(_WIN32) && (_WIN32_WINNT < 0x0600)
+    /* No inet_pton helper... */
+    memset(&slirp->vprefix_addr6, 0, sizeof(slirp->vprefix_addr6));
+    slirp->vprefix_addr6.s6_addr[0] = 0xfe;
+    slirp->vprefix_addr6.s6_addr[1] = 0xc0;
+    slirp->vprefix_len = 64;
+    slirp->vhost_addr6 = slirp->vprefix_addr6;
+    slirp->vhost_addr6.s6_addr[15] = 0x2;
+#else
+    inet_pton(AF_INET6, "fec0::0", &slirp->vprefix_addr6);
+    slirp->vprefix_len = 64;
+    inet_pton(AF_INET6, "fec0::2", &slirp->vhost_addr6);
+#endif
     if (vhostname) {
         pstrcpy(slirp->client_hostname, sizeof(slirp->client_hostname),
                 vhostname);
@@ -251,8 +266,11 @@ void slirp_cleanup(Slirp *slirp)
     unregister_savevm(NULL, "slirp", slirp);
 
     ip_cleanup(slirp);
+    ip6_cleanup(slirp);
     m_cleanup(slirp);
 
+    g_rand_free(slirp->grand);
+
     g_free(slirp->vdnssearch);
     g_free(slirp->tftp_prefix);
     g_free(slirp->bootp_filename);
@@ -744,6 +762,7 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
         arp_input(slirp, pkt, pkt_len);
         break;
     case ETH_P_IP:
+    case ETH_P_IPV6:
         m = m_get(slirp);
         if (!m)
             return;
@@ -757,8 +776,13 @@ void slirp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
         m->m_data += 2 + ETH_HLEN;
         m->m_len -= 2 + ETH_HLEN;
 
-        ip_input(m);
+        if (proto == ETH_P_IP) {
+            ip_input(m);
+        } else if (proto == ETH_P_IPV6) {
+            ip6_input(m);
+        }
         break;
+
     default:
         break;
     }
@@ -826,6 +850,31 @@ static int if_encap4(Slirp *slirp, struct mbuf *ifm, struct ethhdr *eh,
     }
 }
 
+/* Prepare the IPv6 packet to be sent to the ethernet device. Returns 1 if no
+ * packet should be sent, 0 if the packet must be re-queued, 2 if the packet
+ * is ready to go.
+ */
+static int if_encap6(Slirp *slirp, struct mbuf *ifm, struct ethhdr *eh,
+        uint8_t ethaddr[ETH_ALEN])
+{
+    const struct ip6 *ip6h = mtod(ifm, const struct ip6 *);
+    if (!ndp_table_search(slirp, ip6h->ip_dst, ethaddr)) {
+        if (!ifm->resolution_requested) {
+            ndp_send_ns(slirp, ip6h->ip_dst);
+            ifm->resolution_requested = true;
+            ifm->expiration_date =
+                qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + 1000000000ULL;
+        }
+        return 0;
+    } else {
+        eh->h_proto = htons(ETH_P_IPV6);
+        in6_compute_ethaddr(ip6h->ip_src, eh->h_source);
+
+        /* Send this */
+        return 2;
+    }
+}
+
 /* Output the IP packet to the ethernet device. Returns 0 if the packet must be
  * re-queued.
  */
@@ -849,9 +898,15 @@ int if_encap(Slirp *slirp, struct mbuf *ifm)
         }
         break;
 
+    case IP6VERSION:
+        ret = if_encap6(slirp, ifm, eh, ethaddr);
+        if (ret < 2) {
+            return ret;
+        }
+        break;
+
     default:
-        /* Do not assert while we don't manage IP6VERSION */
-        /* assert(0); */
+        g_assert_not_reached();
         break;
     }