“Site-local” addresses in the fec0::/10 range treated as routable #19978

1. 
   practicalswift commented at 8:29 am on September 19, 2020: contributor

   I noticed that we treat “site-local” addresses in the fec0::/10 range as routable:

   0> ResolveIP("fec0::").IsRoutable()
   1true
   

   According to RFC 3879 (“Deprecating Site Local Addresses”, 2004) fec0::/10 is not meant to be routable: “[…] router implementations SHOULD be configured to prevent routing of this prefix by default”. (Edit: #19985 (comment))

   Tor treats fec0::/10 as an IP range reserved to localhost or local networks:

   0    if (((iph6[0] & 0xfe000000) == 0xfc000000) || /* fc00/7  - RFC4193 */
   1        ((iph6[0] & 0xffc00000) == 0xfe800000) || /* fe80/10 - RFC4291 */
   2        ((iph6[0] & 0xffc00000) == 0xfec00000))   /* fec0/10 D- RFC3879 */
   3      return 1;
   

   Which can be compared to Bitcoin Core:

   0> ResolveIP("fc00::").IsRoutable());
   1false
   2> ResolveIP("fe80::").IsRoutable());
   3false
   4> ResolveIP("fec0::").IsRoutable());
   5true
   

2. practicalswift added the label Bug on Sep 19, 2020
3. fanquake added the label P2P on Sep 19, 2020
4. 
   n-thumann commented at 5:06 pm on September 20, 2020: contributor

   Addressed this issue in #19985 :v:
5. 
   practicalswift commented at 2:51 pm on September 22, 2020: contributor

   More context: #19985 (comment) + #19985 (comment)
6. practicalswift closed this on Jun 30, 2021

   ---

7. DrahtBot locked this on Aug 18, 2022

Contributors
practicalswift n-thumann

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Bug P2P