Parsing of BGP attributes.

proto/bgp/attrs.c

@@ -6,10 +6,220 @@
  *	Can be freely distributed and used under the terms of the GNU GPL.
  */
 
+#define LOCAL_DEBUG
+
 #include "nest/bird.h"
 #include "nest/iface.h"
 #include "nest/protocol.h"
 #include "nest/route.h"
 #include "conf/conf.h"
+#include "lib/resource.h"
+#include "lib/string.h"
+#include "lib/unaligned.h"
 
 #include "bgp.h"
+
+static int bgp_check_origin(byte *a, int len)
+{
+  if (len > 2)
+    return 6;
+  return 0;
+}
+
+static int bgp_check_path(byte *a, int len)
+{
+  while (len)
+    {
+      DBG("Path segment %02x %02x\n", a[0], a[1]);
+      if (len < 2 ||
+	  a[0] != BGP_PATH_AS_SET && a[0] != BGP_PATH_AS_SEQUENCE ||
+	  2*a[1] + 2 > len)
+	return 11;
+      len -= 2*a[1] + 2;
+      a += 2*a[1] + 2;
+    }
+  return 0;
+}
+
+static int bgp_check_next_hop(byte *a, int len)
+{
+  ip_addr addr;
+
+  memcpy(&addr, a, len);
+  if (ipa_classify(ipa_ntoh(addr)) & IADDR_HOST)
+    return 0;
+  else
+    return 8;
+}
+
+struct attr_desc {
+  int expected_length;
+  int expected_flags;
+  int type;
+  int (*validate)(byte *attr, int len);
+};
+
+static struct attr_desc bgp_attr_table[] = {
+  { -1, 0, 0, NULL },							/* Undefined */
+  { 1, BAF_TRANSITIVE, EAF_TYPE_INT, bgp_check_origin },		/* BA_ORIGIN */
+  { -1, BAF_TRANSITIVE, EAF_TYPE_AS_PATH, bgp_check_path },		/* BA_AS_PATH */
+  { 4, BAF_TRANSITIVE, EAF_TYPE_IP_ADDRESS, bgp_check_next_hop },	/* BA_NEXT_HOP */
+  { 4, BAF_OPTIONAL, EAF_TYPE_INT, NULL },				/* BA_MULTI_EXIT_DISC */
+  { 4, BAF_OPTIONAL, EAF_TYPE_INT, NULL },				/* BA_LOCAL_PREF */
+  { 0, BAF_OPTIONAL, EAF_TYPE_OPAQUE, NULL },				/* BA_ATOMIC_AGGR */
+  { 6, BAF_OPTIONAL, EAF_TYPE_OPAQUE, NULL },				/* BA_AGGREGATOR */
+#if 0
+  /* FIXME: Handle community lists */
+  { 0, 0 },								/* BA_COMMUNITY */
+  { 0, 0 },								/* BA_ORIGINATOR_ID */
+  { 0, 0 },								/* BA_CLUSTER_LIST */
+#endif
+};
+
+static int bgp_mandatory_attrs[] = { BA_ORIGIN, BA_AS_PATH, BA_NEXT_HOP };
+
+struct rta *
+bgp_decode_attrs(struct bgp_conn *conn, byte *attr, unsigned int len, struct linpool *pool)
+{
+  struct bgp_proto *bgp = conn->bgp;
+  rta *a = lp_alloc(pool, sizeof(struct rta));
+  unsigned int flags, code, l, errcode, i, type;
+  byte *z, *attr_start;
+  byte seen[256/8];
+  eattr *e;
+  ea_list *ea;
+  struct adata *ad;
+  neighbor *neigh;
+  ip_addr nexthop;
+
+  a->proto = &bgp->p;
+  a->source = RTS_BGP;
+  a->scope = SCOPE_UNIVERSE;
+  a->cast = RTC_UNICAST;
+  a->dest = RTD_ROUTER;
+  a->flags = 0;
+  a->aflags = 0;
+  a->from = bgp->cf->remote_ip;
+  a->eattrs = NULL;
+
+  /* Parse the attributes */
+  bzero(seen, sizeof(seen));
+  DBG("BGP: Parsing attributes\n");
+  while (len)
+    {
+      if (len < 2)
+	goto malformed;
+      attr_start = attr;
+      flags = *attr++;
+      code = *attr++;
+      len -= 2;
+      if (flags & BAF_EXT_LEN)
+	{
+	  if (len < 2)
+	    goto malformed;
+	  l = get_u16(attr);
+	  attr += 2;
+	  len -= 2;
+	}
+      else
+	{
+	  if (len < 1)
+	    goto malformed;
+	  l = *attr++;
+	  len--;
+	}
+      if (l > len)
+	goto malformed;
+      len -= l;
+      z = attr;
+      attr += l;
+      DBG("Attr %02x %02x %d\n", code, flags, l);
+      if (seen[code/8] & (1 << (code%8)))
+	goto malformed;
+      seen[code/8] |= (1 << (code%8));
+      if (code && code < sizeof(bgp_attr_table)/sizeof(bgp_attr_table[0]))
+	{
+	  struct attr_desc *desc = &bgp_attr_table[code];
+	  if (desc->expected_length >= 0 && desc->expected_length != (int) l)
+	    { errcode = 5; goto err; }
+	  if ((desc->expected_flags ^ flags) & (BAF_OPTIONAL | BAF_TRANSITIVE))
+	    { errcode = 4; goto err; }
+	  if (desc->validate && (errcode = desc->validate(z, l)))
+	    goto err;
+	  type = desc->type;
+	}
+      else				/* Unknown attribute */
+	{				/* FIXME: Send partial bit when forwarding */
+	  if (!(flags & BAF_OPTIONAL))
+	    { errcode = 2; goto err; }
+	  type = EAF_TYPE_OPAQUE;
+	}
+      ea = lp_alloc(pool, sizeof(struct ea_list) + sizeof(struct eattr));
+      ea->next = a->eattrs;
+      a->eattrs = ea;
+      ea->flags = 0;
+      ea->count = 1;
+      ea->attrs[0].id = EA_CODE(EAP_BGP, code);
+      ea->attrs[0].flags = flags;
+      ea->attrs[0].type = type;
+      if (type & EAF_EMBEDDED)
+	ad = NULL;
+      else
+	{
+	  ad = lp_alloc(pool, sizeof(struct adata) + l);
+	  ea->attrs[0].u.ptr = ad;
+	  ad->length = l;
+	  memcpy(ad->data, z, l);
+	}
+      switch (type)
+	{
+	case EAF_TYPE_ROUTER_ID:
+	case EAF_TYPE_INT:
+	  ea->attrs[0].u.data = get_u32(z);
+	  break;
+	case EAF_TYPE_IP_ADDRESS:
+	  *(ip_addr *)ad->data = ipa_ntoh(*(ip_addr *)ad->data);
+	  break;
+	}
+    }
+
+  /* Check if all mandatory attributes are present */
+  for(i=0; i < sizeof(bgp_mandatory_attrs)/sizeof(bgp_mandatory_attrs[0]); i++)
+    {
+      code = bgp_mandatory_attrs[i];
+      if (!(seen[code/8] & (1 << (code%8))))
+	{
+	  bgp_error(conn, 3, 3, code, 1);
+	  return NULL;
+	}
+    }
+
+  /* Fill in the remaining rta fields */
+  e = ea_find(a->eattrs, EA_CODE(EAP_BGP, BA_NEXT_HOP));
+  ASSERT(e);
+  nexthop = *(ip_addr *) e->u.ptr->data;
+  neigh = neigh_find(&bgp->p, &nexthop, 0);
+  if (!neigh)
+    {
+      if (bgp->cf->multihop)
+	neigh = neigh_find(&bgp->p, &bgp->cf->multihop_via, 0);
+      else
+	neigh = neigh_find(&bgp->p, &bgp->cf->remote_ip, 0);
+    }
+  if (!neigh || !neigh->iface)
+    {
+      DBG("BGP: No route to peer!\n");	/* FIXME */
+      return NULL;
+    }
+  a->gw = neigh->addr;
+  a->iface = neigh->iface;
+  return rta_lookup(a);
+
+malformed:
+  bgp_error(conn, 3, 1, len, 0);
+  return NULL;
+
+err:
+  bgp_error(conn, 3, errcode, code, 0);	/* FIXME: Return attribute data! */
+  return NULL;
+}

proto/bgp/bgp.c

@@ -96,6 +96,8 @@ bgp_close_conn(struct bgp_conn *conn)
     {
       bgp_close(p);
       p->conn = NULL;
+      if (conn->error_flag)		/* FIXME: Enable automatically? */
+	p->p.disabled = 1;
       proto_notify_state(&p->p, PS_DOWN);
     }
 }

proto/bgp/bgp.h

@@ -9,11 +9,14 @@
 #ifndef _BIRD_BGP_H_
 #define _BIRD_BGP_H_
 
+struct linpool;
+
 struct bgp_config {
   struct proto_config c;
   unsigned int local_as, remote_as;
   ip_addr remote_ip;
   int multihop;				/* Number of hops if multihop */
+  ip_addr multihop_via;			/* Multihop: address to route to */
   unsigned connect_retry_time;
   unsigned hold_time, initial_hold_time;
   unsigned keepalive_time;
@@ -63,6 +66,8 @@ void bgp_close_conn(struct bgp_conn *c);
 
 /* attrs.c */
 
+struct rta *bgp_decode_attrs(struct bgp_conn *conn, byte *a, unsigned int len, struct linpool *pool);
+
 /* packets.c */
 
 void bgp_schedule_packet(struct bgp_conn *conn, int type);
@@ -88,7 +93,7 @@ int bgp_rx(struct birdsock *sk, int size);
 #define BA_AS_PATH		0x02				/* WM */
 #define BA_NEXT_HOP		0x03				/* WM */
 #define BA_MULTI_EXIT_DISC	0x04				/* ON */
-#define BA_LOCAL_PREF		0x05				/* WM */
+#define BA_LOCAL_PREF		0x05				/* WD */
 #define BA_ATOMIC_AGGR		0x06				/* WD */
 #define BA_AGGREGATOR		0x07				/* OT */
 #define BA_COMMUNITY		0x08	/* [RFC1997] */		/* OT */
@@ -102,6 +107,9 @@ int bgp_rx(struct birdsock *sk, int size);
 #define BA_MP_UNREACH_NLRI	0x0f
 #define BA_EXTENDED_COMM	0x10	/* draft-ramachandra-bgp-ext-communities */
 
+#define BGP_PATH_AS_SET		1	/* Types of path segments */
+#define BGP_PATH_AS_SEQUENCE	2
+
 /* BGP states */
 
 #define BS_IDLE			0

proto/bgp/config.Y

@@ -15,7 +15,7 @@ CF_HDR
 CF_DECLS
 
 CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY, KEEPALIVE,
-	MULTIHOP, STARTUP)
+	MULTIHOP, STARTUP, VIA)
 
 CF_GRAMMAR
 
@@ -46,7 +46,7 @@ bgp_proto:
  | bgp_proto STARTUP HOLD TIME NUM ';' { BGP_CFG->initial_hold_time = $5; }
  | bgp_proto CONNECT RETRY TIME NUM ';' { BGP_CFG->connect_retry_time = $5; }
  | bgp_proto KEEPALIVE TIME NUM ';' { BGP_CFG->connect_retry_time = $4; }
- | bgp_proto MULTIHOP NUM ';' { BGP_CFG->multihop = $3; }
+ | bgp_proto MULTIHOP NUM VIA IPA ';' { BGP_CFG->multihop = $3; BGP_CFG->multihop_via = $5; }
  ;
 
 CF_CODE

proto/bgp/packets.c

@@ -218,24 +218,26 @@ bgp_rx_open(struct bgp_conn *conn, byte *pkt, int len)
 #define DECODE_PREFIX(pp, ll) do {		\
   int b = *pp++;				\
   int q;					\
-  ip_addr temp;					\
   ll--;						\
   if (b > BITS_PER_IP_ADDRESS) { bgp_error(conn, 3, 10, b, 0); return; } \
   q = (b+7) / 8;				\
-  if (ll < q) goto too_small;			\
+  if (ll < q) goto malformed;			\
-  memcpy(&temp, pp, q);				\
+  memcpy(&prefix, pp, q);			\
   pp += q;					\
   ll -= q;					\
-  n.n.prefix = ipa_and(ipa_ntoh(temp), ipa_mkmask(b));	\
+  prefix = ipa_and(ipa_ntoh(prefix), ipa_mkmask(b)); \
-  n.n.pxlen = b;				\
+  pxlen = b;					\
 } while (0)
+/* FIXME: Check validity of prefixes */
 
 static void
 bgp_rx_update(struct bgp_conn *conn, byte *pkt, int len)
 {
+  struct bgp_proto *bgp = conn->bgp;
   byte *withdrawn, *attrs, *nlri;
-  int withdrawn_len, attr_len, nlri_len;
+  ip_addr prefix;
-  net n;
+  int withdrawn_len, attr_len, nlri_len, pxlen;
+  net *n;
   rte e;
 
   DBG("BGP: UPDATE\n");
@@ -246,45 +248,54 @@ bgp_rx_update(struct bgp_conn *conn, byte *pkt, int len)
   /* Find parts of the packet and check sizes */
   if (len < 23)
     {
-    too_small:
       bgp_error(conn, 1, 2, len, 2);
       return;
     }
   withdrawn = pkt + 21;
   withdrawn_len = get_u16(pkt + 19);
   if (withdrawn_len + 23 > len)
-    goto too_small;
+    {
+    malformed:
+      bgp_error(conn, 3, 1, len, 0);
+      return;
+    }
   attrs = withdrawn + withdrawn_len + 2;
   attr_len = get_u16(attrs - 2);
   if (withdrawn_len + attr_len + 23 > len)
-    goto too_small;
+    goto malformed;
   nlri = attrs + attr_len;
   nlri_len = len - withdrawn_len - attr_len - 23;
   if (!attr_len && nlri_len)
-    goto too_small;
+    goto malformed;
   DBG("Sizes: withdrawn=%d, attrs=%d, NLRI=%d\n", withdrawn_len, attr_len, nlri_len);
 
   /* Withdraw routes */
   while (withdrawn_len)
     {
       DECODE_PREFIX(withdrawn, withdrawn_len);
-      DBG("Withdraw %I/%d\n", n.n.prefix, n.n.pxlen);
+      DBG("Withdraw %I/%d\n", prefix, pxlen);
+      if (n = net_find(bgp->p.table, prefix, pxlen))
+	rte_update(bgp->p.table, n, &bgp->p, NULL);
     }
 
   if (nlri_len)
     {
-#if 0
       rta *a = bgp_decode_attrs(conn, attrs, attr_len, bgp_linpool);
-      if (a)
+      if (!a)
-#endif
+	return;
+      while (nlri_len)
 	{
-	  while (nlri_len)
+	  rte *e;
-	    {
+	  DECODE_PREFIX(nlri, nlri_len); /* FIXME: Uncache rta ! */
-	      DECODE_PREFIX(nlri, nlri_len);
+	  DBG("Add %I/%d\n", prefix, pxlen);
-	      DBG("Add %I/%d\n", n.n.prefix, n.n.pxlen);
+	  e = rte_get_temp(a);
-	    }
+	  n = net_get(bgp->p.table, prefix, pxlen);
+	  e->net = n;
+	  e->pflags = 0;
+	  rte_update(bgp->p.table, n, &bgp->p, e);
 	}
       lp_flush(bgp_linpool);
+      rta_free(a);
     }
 }