The proxies::forwarded::Forwarded::parse method currently (i'm using version 2.11.1) assumes, that all for= items are at the beginning of the forwarding header. As far as i can see from https://datatracker.ietf.org/doc/html/rfc7239#page-5 the RFC does not specify a specific position for the for= forwarded-pair.