Why does core send its own addr message to inbound connections?

[Coding Enthusiast]

Although the code seems to be sending addr message to outbound connections (ref) but in my experience it is sending it to inbound connections too.
And in both cases I can't think of why it is doing that. When the connection is made specially if it is initiated by the other node, they should know our address and sending it again seems pointless to me.
On top of that the addr message is sent after version message (hand-shake) which already contains connection information (ie. the addr message).

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[achow101]

addr messages contain the addresses of other nodes. It's how IP addresses for other nodes are spread around the network.

[Coding Enthusiast]

addr messages contain the addresses of other nodes. It's how IP addresses for other nodes are spread around the network.

That's true most of the times but I'm talking about when nodes send you their own addr message.

Let me put it this way, I connect to 185.132.178.23:18333 (satoshi 0.20.0) and send it a version message saying I know you are 185.132.178.23:18333 (in the receiving node address part), I've also connected to it so I already knew that. Then it sends me its own version message that can contain 185.132.178.23:18333 again (but it doesn't but that's irrelevant for now). After the handshake is finished it sends me an addr message saying 185.132.178.23:18333 is an address of a node!


I'm trying to figure out what the reason behind all this repetition is, specifically the last addr part.

[MixMAx123]

the addr message usually contains all known nodes.
My guess is that the node only knows your own address at the time.

[gmaxwell]

This is how you advertise yourself. When you send the addr message to your peer it will (sometimes) pass it on to other hosts so that they learn about you.

they should know our address and sending it again seems pointless to me.

Yes, they might know about it (or they might have just had it manually configured w/ an addnode), but even if they do their knoweldge doesn't serve the purpose of causing your address to get advertised to the network. For that to happen, you have to advertise it.