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BIP155: mention IPv4-in-IPv6 range MUST NOT be sent within IPV6 - #2234

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brunoerg:2026-08-bip155
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BIP155: mention IPv4-in-IPv6 range MUST NOT be sent within IPV6#2234
brunoerg wants to merge 1 commit into
bitcoin:masterfrom
brunoerg:2026-08-bip155

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@brunoerg

@brunoerg brunoerg commented Aug 3, 2026

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There was a discrepancy between Bitcoin Core and btcd - that I noticed with bitcoinfuzz - about the rejection of IPv4-in-IPv6 when parsing an addrv2 message. btcd ended up implemented the same behavior while it raised a discussion about this not being mentioned in the BIP.

Rejecting this kind of addresses is important for canonical encoding. The whole point of this BIP is having exactly one representation for each network. Besided that, there are other reasons such as reachability accounting, defense against evasion/bypassing address‑type policy, etc.

That said, this PR changes BIP155 to document the behavior where IPv4 addresses embedded in IPv6 should be rejected.

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brunoerg commented Aug 3, 2026

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cc @kcalvinalvin

@jonatack jonatack added Proposed BIP modification PR by non-owner to update BIP content Pending acceptance This BIP modification requires sign-off by the champion of the BIP being modified labels Aug 3, 2026
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Pending acceptance This BIP modification requires sign-off by the champion of the BIP being modified Proposed BIP modification PR by non-owner to update BIP content

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