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Merge pull request #907 from vasild/bip155_clarifications

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BIP155: include changes from followup discussions
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Luke Dashjr 2020-09-23 12:49:25 +00:00 committed by GitHub
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@ -78,8 +78,8 @@ This means that the message contains a serialized <code>std::vector</code> of th
One message can contain up to 1,000 addresses. Clients SHOULD reject messages with more addresses.
Field <code>addr</code> has a variable length, with a maximum of 32 bytes (256 bits). Clients SHOULD reject
longer addresses.
Field <code>addr</code> has a variable length, with a maximum of 512 bytes (4096 bits).
Clients SHOULD reject messages with longer addresses, irrespective of the network ID.
The list of reserved network IDs is as follows:
@ -120,21 +120,23 @@ The list of reserved network IDs is as follows:
| Cjdns overlay network address
|}
To allow for future extensibility, clients MUST ignore address types that they do not know about.
Client MAY store and gossip address formats that they do not know about. Further network ID numbers MUST be reserved in a new BIP document.
Clients are RECOMMENDED to gossip addresses from all known networks even if they are currently not connected to some of them. That could help multi-homed nodes and make it more difficult for an observer to tell which networks a node is connected to.
Clients SHOULD reject addresses that have a different length than specified in this table for a specific address ID, as these are meaningless.
Clients SHOULD NOT gossip addresses from unknown networks because they have no means to validate those addresses and so can be tricked to gossip invalid addresses.
Further network ID numbers MUST be reserved in a new BIP document.
Clients SHOULD reject messages that contain addresses that have a different length than specified in this table for a specific network ID, as these are meaningless.
See the appendices for the address encodings to be used for the various networks.
==Compatibility==
==Signaling support and compatibility==
Send <code>addrv2</code> messages only, and exclusively, when the peer has a certain protocol version (or higher):
<source lang="c++">
//! gossiping using `addrv2` messages starts with this version
static const int GOSSIP_ADDRV2_VERSION = 70016;
</source>
For older peers keep sending the legacy <code>addr</code> message, ignoring addresses with the newly introduced address types.
Introduce a new message type <code>sendaddrv2</code>. Sending such a message indicates that a node can understand and prefers to receive <code>addrv2</code> messages instead of <code>addr</code> messages. I.e. "Send me addrv2".
<code>sendaddrv2</code> SHOULD be sent after receiving the <code>verack</code> message from the peer.
For older peers, that did not emit <code>sendaddrv2</code>, keep sending the legacy <code>addr</code> message, ignoring addresses with the newly introduced address types.
==Reference implementation==