From 1b8cb12cb4e85703102de8e464c66603e1766c23 Mon Sep 17 00:00:00 2001
From: Benjamin Cama <benoar@dolka.fr>
Date: Tue, 19 Jul 2011 15:15:40 +0200
Subject: [PATCH] Add Optional Parameter and Capability handling.

Optional Parameters is defined in RFC4271 and Capability advertisement in
RFC3392. For now, we only hande them upon receiving an OPEN message.

Signed-off-by: Benjamin Cama <benoar@dolka.fr>
---
 bgp.c | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 bgp.h | 17 +++++++++++++++
 2 files changed, 84 insertions(+), 2 deletions(-)

diff --git a/bgp.c b/bgp.c
index 6a868fa..d7701be 100644
--- a/bgp.c
+++ b/bgp.c
@@ -902,6 +902,11 @@ static int bgp_handle_input(struct bgp_peer *peer)
 	    struct bgp_data_open data;
 	    int hold;
 	    int i;
+	    off_t param_offset, capability_offset;
+	    struct bgp_opt_param *param;
+	    uint8_t capabilities_len;
+	    char *capabilities = NULL;
+	    struct bgp_capability *capability;
 
 	    for (i = 0; i < sizeof(p->header.marker); i++)
 	    {
@@ -964,10 +969,70 @@ static int bgp_handle_input(struct bgp_peer *peer)
 	    if (peer->keepalive * 3 > peer->hold)
 		peer->keepalive = peer->hold / 3;
 
+	    /* check for optional parameters */
+	    /* 2 is for the size of type + len (both uint8_t) */
+	    for (param_offset = 0;
+		    param_offset < data.opt_len;
+		    param_offset += 2 + param->len)
+	    {
+		param = (struct bgp_opt_param *)(&data.opt_params + param_offset);
+
+		/* sensible check */
+		if (data.opt_len - param_offset < 2
+			|| param->len > data.opt_len - param_offset - 2) {
+		    LOG(1, 0, 0, "Malformed Optional Parameter list from BGP peer %s\n",
+			peer->name);
+
+		    bgp_send_notification(peer, BGP_ERR_OPEN, BGP_ERR_UNSPEC);
+		    return 0;
+		}
+
+		/* we know only one parameter type */
+		if (param->type != BGP_CAPABILITY_PARAM_TYPE) {
+		    LOG(1, 0, 0, "Unsupported Optional Parameter type %d from BGP peer %s\n",
+			param->type, peer->name);
+
+		    bgp_send_notification(peer, BGP_ERR_OPEN, BGP_ERR_OPN_UNSUP_PARAM);
+		    return 0;
+		}
+
+		capabilities_len = param->len;
+		capabilities = (char *)&param->value;
+	    }
+
+	    /* look for BGP multiprotocol capability */
+	    if (capabilities)
+	    {
+		for (capability_offset = 0;
+			capability_offset < capabilities_len;
+			capability_offset += 2 + capability->len)
+		{
+		    capability = (struct bgp_capability *)(capabilities + capability_offset);
+
+		    /* sensible check */
+		    if (capabilities_len - capability_offset < 2
+			    || capability->len > capabilities_len - capability_offset - 2) {
+			LOG(1, 0, 0, "Malformed Capabilities list from BGP peer %s\n",
+			    peer->name);
+
+			bgp_send_notification(peer, BGP_ERR_OPEN, BGP_ERR_UNSPEC);
+			return 0;
+		    }
+
+		    /* we only know one capability code */
+		    if (capability->code != XXX) {
+			LOG(4, 0, 0, "Unsupported Capability code %d from BGP peer %s\n",
+			    capability->code, peer->name);
+
+			/* TODO: send _which_ capability is unsupported */
+			bgp_send_notification(peer, BGP_ERR_OPEN, BGP_ERR_OPN_UNSUP_CAP);
+			/* we don't terminate, still; we just jump to the next one */
+		    }
+		}
+	    }
+
 	    /* next transition requires an exchange of keepalives */
 	    bgp_send_keepalive(peer);
-
-	    /* FIXME: may need to check for optional params */
 	}
 
 	break;
diff --git a/bgp.h b/bgp.h
index 0a2e59c..beb68f9 100644
--- a/bgp.h
+++ b/bgp.h
@@ -43,6 +43,21 @@ struct bgp_data_open {
     char opt_params[sizeof(((struct bgp_packet *)0)->data) - BGP_DATA_OPEN_SIZE]; /* variable */
 } __attribute__ ((packed));
 
+struct bgp_opt_param {
+    uint8_t type;
+    uint8_t len;
+#define BGP_MAX_OPT_PARAM_SIZE 256
+    char value[BGP_MAX_OPT_PARAM_SIZE];
+} __attribute__ ((packed));
+
+#define BGP_CAPABILITY_PARAM_TYPE 2
+struct bgp_capability {
+    uint8_t code;
+    uint8_t len;
+#define BGP_MAX_CAPABILITY_SIZE 256
+    char value[BGP_MAX_CAPABILITY_SIZE];
+} __attribute__ ((packed));
+
 struct bgp_ip_prefix {
     uint8_t len;
     uint32_t prefix; /* variable */
@@ -101,6 +116,7 @@ struct bgp_data_notification {
 } __attribute__ ((packed));
 
 /* bgp_data_notification.error_code, .error_subcode */
+#define BGP_ERR_UNSPEC			0
 #define BGP_ERR_HEADER			1
 #  define BGP_ERR_HDR_NOT_SYNC		  1
 #  define BGP_ERR_HDR_BAD_LEN		  2
@@ -112,6 +128,7 @@ struct bgp_data_notification {
 #  define BGP_ERR_OPN_UNSUP_PARAM	  4
 #  define BGP_ERR_OPN_AUTH_FAILURE	  5
 #  define BGP_ERR_OPN_HOLD_TIME		  6
+#  define BGP_ERR_OPN_UNSUP_CAP		  7
 #define BGP_ERR_UPDATE			3
 #  define BGP_ERR_UPD_BAD_ATTR_LIST	  1
 #  define BGP_ERR_UPD_UNKN_WK_ATTR	  2
-- 
2.20.1