Relax BGP neighbor parameter

Permit specifying neighbor address, AS number and port independently.
Add 'interface' parameter for specifying interface for link-local
sessions independently.

Thanks to Alexander V. Chernikov for the original patch.

conf/confbase.Y

@@ -72,7 +72,7 @@ CF_DECLS
 %token <t> TEXT
 %type <iface> ipa_scope
 
-%type <i> expr bool pxlen ipa_port
+%type <i> expr bool pxlen
 %type <i32> expr_us
 %type <time> datetime
 %type <a> ipa
@@ -161,14 +161,6 @@ ipa_scope:
  | '%' SYM { $$ = if_get_by_name($2->name); }
  ;
 
-ipa_port:
-   /* empty */ { $$ = 0; }
- | PORT expr {
-     if (($2 < 1) || ($2 > 65535)) cf_error("Invalid port number");
-     $$ = $2;
-   }
- ;
-
 prefix:
    ipa pxlen {
      if (!ip_is_prefix($1, $2)) cf_error("Invalid prefix");

doc/bird.sgml

@@ -1620,10 +1620,20 @@ using the following configuration parameters:
 	address, equivalent to the <cf/source address/ option (see below). This
 	parameter is mandatory.
 
-	<tag>neighbor <m/ip/ [port <m/number/] as <m/number/</tag>
+	<tag>neighbor [<m/ip/] [port <m/number/] [as <m/number/]</tag>
 	Define neighboring router this instance will be talking to and what AS
-	it's located in. In case the neighbor is in the same AS as we are, we
-	automatically switch to iBGP. This parameter is mandatory.
+	it is located in. In case the neighbor is in the same AS as we are, we
+	automatically switch to iBGP. Optionally, the remote port may also be
+	specified. The parameter may be used multiple times with different
+	sub-options (e.g., both <cf/neighbor 10.0.0.1 as 65000;/ and
+	<cf/neighbor 10.0.0.1; neighbor as 65000;/ are valid). This parameter is
+	mandatory.
+
+	<tag>interface <m/string/</tag>
+	Define interface we should use for link-local BGP IPv6 sessions.
+	Interface can also be specified as a part of <cf/neighbor address/
+	(e.g., <cf/neighbor fe80::1234%eth0 as 65000;/). It is an error to use
+	this parameter for non link-local sessions.
 
 	<tag>direct</tag>
 	Specify that the neighbor is directly connected. The IP address of the

proto/bgp/bgp.c

@@ -1196,9 +1196,18 @@ bgp_check_config(struct bgp_config *c)
   if (!c->local_as)
     cf_error("Local AS number must be set");
 
-  if (!c->remote_as)
+  if (ipa_zero(c->remote_ip))
     cf_error("Neighbor must be configured");
 
+  if (!c->remote_as)
+    cf_error("Remote AS number must be set");
+
+  // if (ipa_is_link_local(c->remote_ip) && !c->iface)
+  //   cf_error("Link-local neighbor address requires specified interface");
+
+  if (!ipa_is_link_local(c->remote_ip) != !c->iface)
+    cf_error("Link-local address and interface scope must be used together");
+
   if (!(c->capabilities && c->enable_as4) && (c->remote_as > 0xFFFF))
     cf_error("Neighbor AS number out of range (AS4 not available)");
 

proto/bgp/config.Y

@@ -27,14 +27,15 @@ CF_KEYWORDS(BGP, LOCAL, NEIGHBOR, AS, HOLD, TIME, CONNECT, RETRY,
 	INTERPRET, COMMUNITIES, BGP_ORIGINATOR_ID, BGP_CLUSTER_LIST, IGP,
 	TABLE, GATEWAY, DIRECT, RECURSIVE, MED, TTL, SECURITY, DETERMINISTIC,
 	SECONDARY, ALLOW, BFD, ADD, PATHS, RX, TX, GRACEFUL, RESTART, AWARE,
-	CHECK, LINK)
+	CHECK, LINK, PORT)
 
 CF_GRAMMAR
 
 CF_ADDTO(proto, bgp_proto '}' { bgp_check_config(BGP_CFG); } )
 
 bgp_proto_start: proto_start BGP {
      this_proto = proto_config_new(&proto_bgp, $1);
+     BGP_CFG->remote_port = BGP_PORT;
      BGP_CFG->multihop = -1;	/* undefined */
      BGP_CFG->hold_time = 240;
      BGP_CFG->connect_retry_time = 120;
@@ -56,22 +57,25 @@ bgp_proto_start: proto_start BGP {
  }
  ;
 
+bgp_nbr_opts:
+   /* empty */
+ | bgp_nbr_opts PORT expr { BGP_CFG->remote_port = $3; if (($3<1) || ($3>65535)) cf_error("Invalid port number");  }
+ | bgp_nbr_opts AS expr { BGP_CFG->remote_as = $3; }
+ ;
+
 bgp_proto:
    bgp_proto_start proto_name '{'
  | bgp_proto proto_item ';'
  | bgp_proto LOCAL AS expr ';' { BGP_CFG->local_as = $4; }
  | bgp_proto LOCAL ipa AS expr ';' { BGP_CFG->source_addr = $3; BGP_CFG->local_as = $5; }
- | bgp_proto NEIGHBOR ipa ipa_scope ipa_port AS expr ';' {
+ | bgp_proto NEIGHBOR bgp_nbr_opts ';'
+ | bgp_proto NEIGHBOR ipa ipa_scope bgp_nbr_opts ';' {
      if (ipa_nonzero(BGP_CFG->remote_ip))
        cf_error("Only one neighbor per BGP instance is allowed");
-     if (!ipa_is_link_local($3) != !$4)
-       cf_error("Link-local address and interface scope must be used together");
-
      BGP_CFG->remote_ip = $3;
-     BGP_CFG->iface = $4;
-     BGP_CFG->remote_port = ($5 > 0) ? $5 : BGP_PORT;
-     BGP_CFG->remote_as = $7;
+     if ($4) BGP_CFG->iface = $4;
    }
+ | bgp_proto INTERFACE TEXT ';' { BGP_CFG->iface = if_get_by_name($3); }
  | bgp_proto RR CLUSTER ID idval ';' { BGP_CFG->rr_cluster_id = $5; }
  | bgp_proto RR CLIENT ';' { BGP_CFG->rr_client = 1; }
  | bgp_proto RS CLIENT ';' { BGP_CFG->rs_client = 1; }