ChaCha20-Poly1305 auth tag failure

[Will Cosgrove]

Hi All,
I’m implementing ChaCha20-Poly1305 in an OS ssh client library libssh2 (https://github.com/libssh2/libssh2). I’m using the ChaCha related files from OpenSSH with very minimal modifications.  I have it working connecting to sshd, but every ~2 million packets I'll get a random auth tag failure when downloading files (the last 4 bytes don’t match).

I know this borderline off-topic, but if I could bend the ear of the implementer of the ChaCha20 support off-list that’d be great. I’d really like to get this working 100% but I’m running out of ideas.

Thanks in advance,

Will