Subject: Re: [bitcoin-dev] BIP proposal - addrv2 message

From: Gregory Maxwell <[email-masked]>
Date: Wed, 6 Mar 2019 03:02:51 +0000

On Wed, Mar 6, 2019 at 12:22 AM Wladimir J. van der Laan via
bitcoin-dev <[email-masked]> wrote:
> Field <code>addr</code> has a variable length, with a maximum of 32 bytes (256 bits). Clients SHOULD reject
> longer addresses.

Is 32 bytes long enough for I2P?  It seems like there are two formats,
is there a reason we might want to use the longer one?
https://geti2p.net/en/docs/naming

Probably the spec should define the limit per address type (e.g.
sending a 32 byte IPv4 makes no sense).   And either a maximum for ANY
type (so that 1000*largest size is reasonable), or a maximum size for
the message (e.g. regardless of the included size, an add message
should never be over, say 100k).

> * ''Client MAY store and gossip address formats that they do not know about'': does it ever make sense to gossip addresses outside a certain overlay network? Say, I2P addresses to Tor? I'm not sure. Especially for networks that have no exit nodes as there is no overlap with the globally routed internet at all.

I think clients should be discouraged from gossiping stuff they cannot
test but not forbidden from doing so. Separately, they should be
strongly discouraged from gossiping types they don't understand at
all. We don't really want to see people doing file xfer over invalid
addr types. :)