net: align v2 message type validation with v1 range #35958

1. 
   brunoerg commented at 1:13 PM on August 12, 2026: contributor

   BIP324 specifies the 13-byte long-form message type encoding as "an ASCII message type (as in the v1 P2P protocol)", but V2Transport::GetMessageType() accepted bytes up to 0x7F, while for V1 it only accepts printable ASCII (0x20-0x7E).

   This changes V2 to match V1 on it and add test coverage.

2. net: align v2 message type validation with v1 range

   BIP324 specifies the 13-byte long-form message type encoding as
   "an ASCII message type (as in the v1 P2P protocol)", but
   V2Transport::GetMessageType() accepted bytes up to 0x7F, while
   for V1 it only accepts printable ASCII (0x20-0x7E).
   
   This changes V2 to match V1 on it and add test coverage.

   cc577de954
3. DrahtBot added the label P2P on Aug 12, 2026
4. 
   DrahtBot commented at 1:13 PM on August 12, 2026: contributor

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   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/35958.

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   ACK	nervana21, w0xlt, sedited, ajtowns

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5. 
   nervana21 commented at 8:56 PM on August 12, 2026: contributor

   tACK cc577de954671378268bab2a78714869b4f7388d

   The changes match CMessageHeader::IsMessageTypeValid and BIP324's "ASCII as in v1" wording.

6. 
   w0xlt commented at 6:33 PM on August 13, 2026: contributor

   ACK cc577de954671378268bab2a78714869b4f7388d

7. fanquake requested review from mzumsande on Aug 14, 2026
8. sedited requested review from ajtowns on Aug 29, 2026
9. 
   ajtowns commented at 9:41 AM on August 29, 2026: contributor

   The "space to tilde" range has been consistent in v1 since the satoshi days, so seems reasonable. Ultimately just gives a different error ("invalid message type" from net.h rather than "Unknown message type" from net_processing with the unsafe chars skipped), and would be reverted if for some reason we wanted to support a message type with weird characters.

   utACK ca7162cde58e69214a3309c17fac6d666b5f055a

10. sedited approved
11. 
    sedited commented at 12:31 PM on August 29, 2026: contributor

    ACK cc577de954671378268bab2a78714869b4f7388d

12. 
    sedited commented at 12:43 PM on August 29, 2026: contributor

    @ajtowns you ACKed a commit different from the head, was that a mis-paste?

13. 
    ajtowns commented at 12:29 AM on September 3, 2026: contributor

    @ajtowns you ACKed a commit different from the head, was that a mis-paste?

    Yeah, that was current master.

    utACK cc577de954671378268bab2a78714869b4f7388d

14. fanquake merged this on Sep 3, 2026
15. fanquake closed this on Sep 3, 2026

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Review Requested
ajtownsmzumsande