Implements Router Advertisement protocol.

1 files changed, 268 insertions, 0 deletions

diff --git a/proto/radv/packets.c b/proto/radv/packets.c
new file mode 100644
index 00000000..8aa487b0
--- /dev/null
+++ b/proto/radv/packets.c
@@ -0,0 +1,268 @@
+/*
+ *	BIRD -- RAdv Packet Processing
+ *
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+
+#include <stdlib.h>
+#include "radv.h"
+
+struct radv_ra_packet
+{
+  u8 type;
+  u8 code;
+  u16 checksum;
+  u8 current_hop_limit;
+  u8 flags;
+  u16 router_lifetime;
+  u32 reachable_time;
+  u32 retrans_timer;
+};
+
+#define OPT_RA_MANAGED 0x80
+#define OPT_RA_OTHER_CFG 0x40
+
+#define OPT_PREFIX 3
+#define OPT_MTU 5
+
+struct radv_opt_prefix
+{
+  u8 type;
+  u8 length;
+  u8 pxlen;
+  u8 flags;
+  u32 valid_lifetime;
+  u32 preferred_lifetime;
+  u32 reserved;
+  ip_addr prefix;
+};
+
+#define OPT_PX_ONLINK 0x80
+#define OPT_PX_AUTONOMOUS 0x40
+
+struct radv_opt_mtu
+{
+  u8 type;
+  u8 length;
+  u16 reserved;
+  u32 mtu;
+};
+
+static struct radv_prefix_config default_prefix = {
+  .onlink = 1,
+  .autonomous = 1,
+  .valid_lifetime = DEFAULT_VALID_LIFETIME,
+  .preferred_lifetime = DEFAULT_PREFERRED_LIFETIME
+};
+
+static struct radv_prefix_config *
+radv_prefix_match(struct radv_iface *ifa, struct ifa *a)
+{
+  struct proto *p = &ifa->ra->p;
+  struct radv_config *cf = (struct radv_config *) (p->cf);
+  struct radv_prefix_config *pc;
+
+  if (a->scope <= SCOPE_LINK)
+    return NULL;
+
+  WALK_LIST(pc, ifa->cf->pref_list)
+    if ((a->pxlen >= pc->pxlen) && ipa_in_net(a->prefix, pc->prefix, pc->pxlen))
+      return pc;
+
+  WALK_LIST(pc, cf->pref_list)
+    if ((a->pxlen >= pc->pxlen) && ipa_in_net(a->prefix, pc->prefix, pc->pxlen))
+      return pc;
+
+  return &default_prefix;
+}
+
+static void
+radv_prepare_ra(struct radv_iface *ifa)
+{
+  struct proto_radv *ra = ifa->ra;
+
+  char *buf = ifa->sk->tbuf;
+  char *bufstart = buf;
+  char *bufend = buf + ifa->sk->tbsize;
+
+  struct radv_ra_packet *pkt = (void *) buf;
+  pkt->type = ICMPV6_RA;
+  pkt->code = 0;
+  pkt->checksum = 0;
+  pkt->current_hop_limit = ifa->cf->current_hop_limit;
+  pkt->flags = (ifa->cf->managed ? OPT_RA_MANAGED : 0) |
+    (ifa->cf->other_config ? OPT_RA_OTHER_CFG : 0);
+  pkt->router_lifetime = htons(ifa->cf->default_lifetime);
+  pkt->reachable_time = htonl(ifa->cf->reachable_time);
+  pkt->retrans_timer = htonl(ifa->cf->retrans_timer);
+  buf += sizeof(*pkt);
+
+  if (ifa->cf->link_mtu)
+  {
+    struct radv_opt_mtu *om = (void *) buf;
+    om->type = OPT_MTU;
+    om->length = 1;
+    om->reserved = 0;
+    om->mtu = htonl(ifa->cf->link_mtu);
+    buf += sizeof (*om);
+  }
+
+  struct ifa *addr;
+  WALK_LIST(addr, ifa->iface->addrs)
+  {
+    struct radv_prefix_config *pc;
+    pc = radv_prefix_match(ifa, addr);
+
+    if (!pc || pc->skip)
+      continue;
+
+    if (buf + sizeof(struct radv_opt_prefix) > bufend)
+    {
+      log(L_WARN "%s: Too many prefixes on interface %s", ra->p.name, ifa->iface->name);
+      break;
+    }
+
+    struct radv_opt_prefix *op = (void *) buf;
+    op->type = OPT_PREFIX;
+    op->length = 4;
+    op->pxlen = addr->pxlen;
+    op->flags = (pc->onlink ? OPT_PX_ONLINK : 0) |
+      (pc->autonomous ? OPT_PX_AUTONOMOUS : 0);
+    op->valid_lifetime = htonl(pc->valid_lifetime);
+    op->preferred_lifetime = htonl(pc->preferred_lifetime);
+    op->reserved = 0;
+    op->prefix = addr->prefix;
+    ipa_hton(op->prefix);
+    buf += sizeof(*op);
+  }
+  
+  ifa->plen = buf - bufstart;
+}
+
+
+void
+radv_send_ra(struct radv_iface *ifa, int shutdown)
+{
+  struct proto_radv *ra = ifa->ra;
+
+  /* We store prepared RA in tbuf */
+  if (!ifa->plen)
+    radv_prepare_ra(ifa);
+
+  if (shutdown)
+  {
+    /* Modify router lifetime to 0, it is not restored because
+       we suppose that the iface will be removed */
+    struct radv_ra_packet *pkt = (void *) ifa->sk->tbuf;
+    pkt->router_lifetime = 0;
+  }
+
+  RADV_TRACE(D_PACKETS, "Sending RA via %s", ifa->iface->name);
+  sk_send_to(ifa->sk, ifa->plen, AllNodes, 0);
+}
+
+
+static int
+radv_rx_hook(sock *sk, int size)
+{
+  struct radv_iface *ifa = sk->data;
+  struct proto_radv *ra = ifa->ra;
+
+  /* We want just packets from sk->iface */
+  if (sk->lifindex != sk->iface->index)
+    return 1;
+
+  if (ipa_equal(sk->faddr, ifa->addr->ip))
+    return 1;
+
+  if (size < 8)
+    return 1;
+
+  byte *buf = sk->rbuf;
+
+  if (buf[1] != 0)
+    return 1;
+
+  /* Validation is a bit sloppy - Hop Limit is not checked and
+     length of options is ignored for RS and left to later for RA */
+
+  switch (buf[0])
+  {
+  case ICMPV6_RS:
+    RADV_TRACE(D_PACKETS, "Received RS from %I via %s",
+	       sk->faddr, ifa->iface->name);
+    radv_iface_notify(ifa, RA_EV_RS);
+    return 1;
+
+  case ICMPV6_RA:
+    RADV_TRACE(D_PACKETS, "Received RA from %I via %s",
+	       sk->faddr, ifa->iface->name);
+    /* FIXME - there should be some checking of received RAs, but we just ignore them */
+    return 1;
+
+  default:
+    return 1;
+  }
+}
+
+static void
+radv_tx_hook(sock *sk)
+{
+  struct radv_iface *ifa = sk->data;
+  log(L_WARN "%s: TX hook called", ifa->ra->p.name);
+}
+
+static void
+radv_err_hook(sock *sk, int err)
+{
+  struct radv_iface *ifa = sk->data;
+  log(L_ERR "%s: Socket error: %m", ifa->ra->p.name, err);
+}
+
+int
+radv_sk_open(struct radv_iface *ifa)
+{
+  sock *sk = sk_new(ifa->ra->p.pool);
+  sk->type = SK_IP;
+  sk->dport = ICMPV6_PROTO;
+  sk->saddr = IPA_NONE;
+
+  sk->ttl = 255; /* Mandatory for Neighbor Discovery packets */
+  sk->rx_hook = radv_rx_hook;
+  sk->tx_hook = radv_tx_hook;
+  sk->err_hook = radv_err_hook;
+  sk->iface = ifa->iface;
+  sk->rbsize = 1024; // bufsize(ifa);
+  sk->tbsize = 1024; // bufsize(ifa);
+  sk->data = ifa;
+  sk->flags = SKF_LADDR_RX;
+
+  if (sk_open(sk) != 0)
+    goto err;
+
+  sk->saddr = ifa->addr->ip;
+
+  /* 2 is an offset of the checksum in an ICMPv6 packet */
+  if (sk_set_ipv6_checksum(sk, 2) < 0)
+    goto err;
+
+  /* We want listen just to ICMPv6 messages of type RS and RA */
+  if (sk_set_icmp_filter(sk, ICMPV6_RS, ICMPV6_RA) < 0)
+    goto err;
+
+  if (sk_setup_multicast(sk) < 0)
+    goto err;
+
+  if (sk_join_group(sk, AllRouters) < 0)
+    goto err;
+
+  ifa->sk = sk;
+  return 1;
+
+ err:
+  rfree(sk);
+  return 0;
+}
+