bgpd: Ignore handling NLRIs if we received MP_UNREACH_NLRI

If we receive MP_UNREACH_NLRI, we should stop handling remaining NLRIs if
no mandatory path attributes received.

In other words, if MP_UNREACH_NLRI received, the remaining NLRIs should be handled
as a new data, but without mandatory attributes, it's a malformed packet.

In normal case, this MUST not happen at all, but to avoid crashing bgpd, we MUST
handle that.

Reported-by: Iggy Frankovic <iggyfran@amazon.com>
Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>
(cherry picked from commit c37119df45bbf4ef713bc10475af2ee06e12f3bf)

diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c
index 638546ed21851f3d9971974ffd923b85d292a87f..56e77eb3a78752bf864c6ef3888f84c28e8c30aa 100644 (file)
--- a/bgpd/bgp_attr.c
+++ b/bgpd/bgp_attr.c
@@ -3399,15 +3399,6 @@ static int bgp_attr_check(struct peer *peer, struct attr *attr,
            !length)
                return BGP_ATTR_PARSE_WITHDRAW;
 
-       /* "An UPDATE message that contains the MP_UNREACH_NLRI is not required
-          to carry any other path attributes.", though if MP_REACH_NLRI or NLRI
-          are present, it should.  Check for any other attribute being present
-          instead.
-        */
-       if ((!CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_REACH_NLRI)) &&
-            CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_UNREACH_NLRI))))
-               return BGP_ATTR_PARSE_PROCEED;
-
        if (!CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_ORIGIN)))
                type = BGP_ATTR_ORIGIN;
 
@@ -3426,6 +3417,16 @@ static int bgp_attr_check(struct peer *peer, struct attr *attr,
            && !CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_LOCAL_PREF)))
                type = BGP_ATTR_LOCAL_PREF;
 
+       /* An UPDATE message that contains the MP_UNREACH_NLRI is not required
+        * to carry any other path attributes. Though if MP_REACH_NLRI or NLRI
+        * are present, it should. Check for any other attribute being present
+        * instead.
+        */
+       if (!CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_REACH_NLRI)) &&
+           CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_UNREACH_NLRI)))
+               return type ? BGP_ATTR_PARSE_MISSING_MANDATORY
+                           : BGP_ATTR_PARSE_PROCEED;
+
        /* If any of the well-known mandatory attributes are not present
         * in an UPDATE message, then "treat-as-withdraw" MUST be used.
         */

diff --git a/bgpd/bgp_attr.h b/bgpd/bgp_attr.h
index fc347e7a1b4b922407fd7b9e55422e6d348cc0fc..d30155e6dba0a8210198393ed2c0c0b741e6d7a2 100644 (file)
--- a/bgpd/bgp_attr.h
+++ b/bgpd/bgp_attr.h
@@ -364,6 +364,7 @@ enum bgp_attr_parse_ret {
        /* only used internally, send notify + convert to BGP_ATTR_PARSE_ERROR
         */
        BGP_ATTR_PARSE_ERROR_NOTIFYPLS = -3,
+       BGP_ATTR_PARSE_MISSING_MANDATORY = -4,
 };
 
 struct bpacket_attr_vec_arr;

diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 8fbdce56a2b69b7a82a0d7d244e4071c087bf6a2..cae82cbbb77fdd1dbe20ccd02cec3cee3c3ded80 100644 (file)
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -2165,7 +2165,12 @@ static int bgp_update_receive(struct peer_connection *connection,
        /* Network Layer Reachability Information. */
        update_len = end - stream_pnt(s);
 
-       if (update_len && attribute_len) {
+       /* If we received MP_UNREACH_NLRI attribute, but also NLRIs, then
+        * NLRIs should be handled as a new data. Though, if we received
+        * NLRIs without mandatory attributes, they should be ignored.
+        */
+       if (update_len && attribute_len &&
+           attr_parse_ret != BGP_ATTR_PARSE_MISSING_MANDATORY) {
                /* Set NLRI portion to structure. */
                nlris[NLRI_UPDATE].afi = AFI_IP;
                nlris[NLRI_UPDATE].safi = SAFI_UNICAST;