Too many P2P connections from old Geth/Erigon version.

[zzzckck]

Description

The latest BSC hardfork is Tycho&Haber, which is supported by

• Geth: https://github.com/bnb-chain/bsc/releases/tag/v1.4.8
• Erigon: https://github.com/node-real/bsc-erigon/releases/tag/v1.2.9

But I noticed that my nodes are connected with lots of old Geth/Erigon release, especially Geth-v1.3.13, Erigon-v1.2.5. These old version does not support the latest hard fork, and they are supposed to be rejected due to mismatch forkid.

I dumped my connected peers for reference: peers_0808.log

# cat peers_0808.log|grep "name: "
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "Geth/v1.4.12-83a9b137-20240724/linux-amd64/go1.21.1",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "Geth/v1.4.12-83a9b137/linux-arm64/go1.21.6",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "Geth/v1.4.10-f0c77955-20240621/linux-amd64/go1.21.11",
    name: "Geth/v1.4.8/linux-amd64/go1.22.3",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "Geth/v1.4.8-5bbc44f3-20240723/linux-amd64/go1.22.4",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "Geth/v1.3.10-c8cc9196-20240304/linux-amd64/go1.21.7",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    name: "erigon/v1.2.5/linux-amd64/go1.21.6",
    ...

This issue happens in Erigon client as well, I think it is not expected, create this issue to track

Steps to reproduce the behaviour

Just set up a BSC full node either with Geth-v1.4.12+ or Erigon-v1.2.12+.
After a while, dump your connected peers by: ./bsc --exec "admin.peers" attach geth.ipc > peers.log

Backtrace

NA

[MatusKysel]

so it's because of this rule

//   2. If the remote FORK_CSUM is a subset of the local past forks and the
//      remote FORK_NEXT matches with the locally following fork block number,
//      connect.
//        Remote node is currently syncing. It might eventually diverge from
//        us, but at this current point in time we don't have enough information.

https://github.com/bnb-chain/bsc/blob/develop/core/forkid/forkid.go#L191

[NathanBSC]

checked, agree with @MatusKysel , obey rule #2