Fixes a compatibility issue in OSPFv2 PtP links.

BIRD used zero netmask in hello packets on all PtP links, not just on
unnumbered ones. This patch fixes it and adds option 'ptp netmask'
for overriding the default behavior.

Thanks to Alexander V. Chernikov for the original patch.

doc/bird.sgml

@@ -1940,6 +1940,7 @@ protocol ospf <name> {
 				nonbroadcast|nbma|pointomultipoint|ptmp];
 			strict nonbroadcast <switch>;
 			real broadcast <switch>;
+			ptp netmask <switch>;
 			check link <switch>;
 			ecmp weight <num>;
 			authentication [none|simple|cryptographic];
@@ -2183,6 +2184,18 @@ protocol ospf <name> {
 	 probably is not interoperable with other OSPF
 	 implementations. Default value is no.
 
+	<tag>ptp netmask <m/switch/</tag>
+	 In <cf/type ptp/ network configurations, OSPFv2
+	 implementations should ignore received netmask field in hello
+	 packets and should send hello packets with zero netmask field
+	 on unnumbered PtP links. But some OSPFv2 implementations
+	 perform netmask checking even for PtP links. This option
+	 specifies whether real netmask will be used in hello packets
+	 on <cf/type ptp/ interfaces. You should ignore this option
+	 unless you meet some compatibility problems related to this
+	 issue. Default value is no for unnumbered PtP links, yes
+	 otherwise.
+
 	<tag>check link <M>switch</M></tag>
 	 If set, a hardware link state (reported by OS) is taken into
 	 consideration. When a link disappears (e.g. an ethernet cable is

proto/ospf/config.Y

@@ -131,7 +131,7 @@ CF_KEYWORDS(NONE, SIMPLE, AUTHENTICATION, STRICT, CRYPTOGRAPHIC)
 CF_KEYWORDS(ELIGIBLE, POLL, NETWORKS, HIDDEN, VIRTUAL, CHECK, LINK)
 CF_KEYWORDS(RX, BUFFER, LARGE, NORMAL, STUBNET, HIDDEN, SUMMARY, TAG, EXTERNAL)
 CF_KEYWORDS(WAIT, DELAY, LSADB, ECMP, LIMIT, WEIGHT, NSSA, TRANSLATOR, STABILITY)
-CF_KEYWORDS(GLOBAL, LSID, ROUTER, SELF, INSTANCE, REAL)
+CF_KEYWORDS(GLOBAL, LSID, ROUTER, SELF, INSTANCE, REAL, NETMASK)
 
 %type <t> opttext
 %type <ld> lsadb_args
@@ -290,6 +290,7 @@ ospf_iface_item:
  | TYPE POINTOMULTIPOINT { OSPF_PATT->type = OSPF_IT_PTMP ; }
  | TYPE PTMP { OSPF_PATT->type = OSPF_IT_PTMP ; }
  | REAL BROADCAST bool { OSPF_PATT->real_bcast = $3; if (OSPF_VERSION != 2) cf_error("Real broadcast option requires OSPFv2"); }
+ | PTP NETMASK bool { OSPF_PATT->ptp_netmask = $3; if (OSPF_VERSION != 2) cf_error("Real netmask option requires OSPFv2"); }
  | TRANSMIT DELAY expr { OSPF_PATT->inftransdelay = $3 ; if (($3<=0) || ($3>65535)) cf_error("Transmit delay must be in range 1-65535"); }
  | PRIORITY expr { OSPF_PATT->priority = $2 ; if (($2<0) || ($2>255)) cf_error("Priority must be in range 0-255"); }
  | STRICT NONBROADCAST bool { OSPF_PATT->strictnbma = $3 ; }
@@ -364,6 +365,7 @@ ospf_iface_start:
   OSPF_PATT->type = OSPF_IT_UNDEF;
   init_list(&OSPF_PATT->nbma_list);
   OSPF_PATT->autype = OSPF_AUTH_NONE;
+  OSPF_PATT->ptp_netmask = 2; /* not specified */
   reset_passwords();
  }
 ;

proto/ospf/hello.c

@@ -253,7 +253,8 @@ ospf_hello_send(struct ospf_iface *ifa, int kind, struct ospf_neighbor *dirn)
 #ifdef OSPFv2
   pkt->netmask = ipa_mkmask(ifa->addr->pxlen);
   ipa_hton(pkt->netmask);
-  if ((ifa->type == OSPF_IT_VLINK) || (ifa->type == OSPF_IT_PTP))
+  if ((ifa->type == OSPF_IT_VLINK) ||
+      ((ifa->type == OSPF_IT_PTP) && !ifa->ptp_netmask))
     pkt->netmask = IPA_NONE;
 #endif
 

proto/ospf/iface.c

@@ -537,6 +537,9 @@ ospf_iface_new(struct ospf_area *oa, struct ifa *addr, struct ospf_iface_patt *i
 #ifdef OSPFv2
   ifa->autype = ip->autype;
   ifa->passwords = ip->passwords;
+  ifa->ptp_netmask = !(addr->flags & IA_PEER);
+  if (ip->ptp_netmask < 2)
+    ifa->ptp_netmask = ip->ptp_netmask;
 #endif
 
 #ifdef OSPFv3

proto/ospf/ospf.h

@@ -273,6 +273,7 @@ struct ospf_iface
   u16 rxbuf;			/* Buffer size */
   u8 check_link;		/* Whether iface link change is used */
   u8 ecmp_weight;		/* Weight used for ECMP */
+  u8 ptp_netmask;		/* Send real netmask for P2P */
 };
 
 struct ospf_md5
@@ -810,6 +811,7 @@ struct ospf_iface_patt
   u8 check_link;
   u8 ecmp_weight;
   u8 real_bcast;		/* Not really used in OSPFv3 */
+  u8 ptp_netmask;		/* bool but 2 for unspecified */
 
 #ifdef OSPFv2
   list *passwords;