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

issue practicalswift opened this issue on September 19, 2020

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:
```
> ResolveIP("fec0::").IsRoutable()
true
```
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:
```
    if (((iph6[0] & 0xfe000000) == 0xfc000000) || /* fc00/7  - RFC4193 */
        ((iph6[0] & 0xffc00000) == 0xfe800000) || /* fe80/10 - RFC4291 */
        ((iph6[0] & 0xffc00000) == 0xfec00000))   /* fec0/10 D- RFC3879 */
      return 1;
```
Which can be compared to Bitcoin Core:
```
> ResolveIP("fc00::").IsRoutable());
false
> ResolveIP("fe80::").IsRoutable());
false
> ResolveIP("fec0::").IsRoutable());
true
```
practicalswift added the label Bug on Sep 19, 2020
fanquake added the label P2P on Sep 19, 2020
n-thumann commented at 5:06 PM on September 20, 2020: contributor

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

More context: #19985 (comment) + #19985 (comment)
practicalswift closed this on Jun 30, 2021
DrahtBot locked this on Aug 18, 2022

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