BIRD patch in useful-patches

Author: schoen

useful-patches/0001-Don-t-treat-0-8-and-240-4-specially-in-IPv4-classifi.patch

@@ -0,0 +1,69 @@
+From 2f223855782a312108019074e3365e29e51c10ce Mon Sep 17 00:00:00 2001
+From: Seth Schoen <schoen@loyalty.org>
+Date: Fri, 18 Nov 2022 15:33:28 -0800
+Subject: [PATCH] Don't treat 0/8 and 240/4 specially in IPv4 classification
+
+With the exception of 0.0.0.0 and 255.255.255.255, which have additional
+special meanings, treat 0/8 and 240/4 as normal unicast addresses by
+default. This is because some people are experimenting with using these
+addresses as regular unicast (either for private addresses or for potential
+future public addresses).
+
+On the public Internet, they would still currently be regarded as bogons and
+one could make (maybe by default) a bogon-filtering rule in bird.conf that
+would not permit these addresses to be routed, e.g. with a pair of static
+routes
+
+route 0.0.0.0/8 prohibit;
+route 240.0.0.0/4 prohibit;
+
+Dave Taht, who wrote a prior version of this patch, suggested that in
+any case it is better to have bogons defined in a configuration file
+than hard-coded in software.
+---
+ lib/ip.c | 7 +++++--
+ lib/ip.h | 2 +-
+ 2 files changed, 6 insertions(+), 3 deletions(-)
+
+diff --git a/lib/ip.c b/lib/ip.c
+index 4c5fa47f..e13bbce0 100644
+--- a/lib/ip.c
++++ b/lib/ip.c
+@@ -87,8 +87,10 @@ ip4_classify(ip4_addr ad)
+ 
+   if (b < 0xe0)
+   {
+-    if (b == 0x00)				/* 0.0.0.0/8        This network */
++    if (a == 0x00000000)			/* 0.0.0.0/32       Unset address */
+       return IADDR_INVALID;
++						/* 0.0.0.0/8 is otherwise reserved, but
++						 * some people are using it or trying to */
+ 
+     if (b == 0x7f)				/* 127.0.0.0/8      Loopback address */
+       return IADDR_HOST | SCOPE_HOST;
+@@ -107,7 +109,8 @@ ip4_classify(ip4_addr ad)
+   if (a == 0xffffffff)				/* 255.255.255.255  Broadcast address */
+     return IADDR_BROADCAST | SCOPE_LINK;
+ 
+-  return IADDR_HOST | SCOPE_SITE;		/* 240.0.0.0/4      Reserved / private */
++  return IADDR_HOST | SCOPE_UNIVERSE;		/* 240.0.0.0/4      Reserved / private, but
++						 * some people are using it or trying to */
+ }
+ 
+ int
+diff --git a/lib/ip.h b/lib/ip.h
+index 9eef2e16..875b9f5e 100644
+--- a/lib/ip.h
++++ b/lib/ip.h
+@@ -245,7 +245,7 @@ static inline int ip6_is_v4mapped(ip6_addr a)
+ #define ipa_is_link_local(x) ip6_is_link_local(x)
+ 
+ static inline int ip4_is_unicast(ip4_addr a)
+-{ return _I(a) < 0xe0000000; }
++{ return _I(a) < 0xe0000000 || (_I(a) >= 0xf0000000 && _I(a) != 0xffffffff); }
+ 
+ /* XXXX remove */
+ static inline int ipa_classify_net(ip_addr a)
+-- 
+2.25.1
+

useful-patches/README.md

@@ -9,3 +9,8 @@ This patch is included with Linux 5.14 and later, and makes the lowest
 address on an IPv4 segment non-broadcast.  You can apply this version
 to a Linux 5.10 LTS kernel (or likely to other kernel versions prior
 to 5.14).
+
+* 0001-Don-t-treat-0-8-and-240-4-specially-in-IPv4-classifi.patch
+
+This patch is for use with the BIRD routing daemon, and increases the
+extent to which it can support Internet routes within 0/8 and 240/4.