This loop does not seem right? While the change is correct (len instead of self.pos), the self.buf bound and the pos increment seems wrong?

I think it would be better to use self.rw.write_all(&self.buf[..len]) instead of hand-rolling it, unless you have a particular reason for hand-rolling the same?

You are right about that, I don't know how I missed that 😅.

The hand-rolling is necessary tho, write_ready signals that the next write will be block-free, but write_all may perform as many writes as it needs.
If we cannot add any check in-between write calls the timeout won't work and the client may get stuck indefinitely depending on the inner writer.

Fair, in that case pos += self.rw.write(&self.buf[pos..len]).or(Err(Error::Write))?;