begin_cell_parse and IPv6
spec about IPV6 inside BEGIN cell -- ADDRPORT is made of ADDRESS | ':' | PORT | [00] where ADDRESS is IPv6 address surrounded by square brackets; and where PORT is a decimal integer between 1 and 65535, inclusive.
begin_cell_parse can't parse IPV6 by tor_addr_port_split correctly. for example [2607:f8b0:4000:800::200e]:80 tor_addr_parse can't handle port and will return corrupted result in this case, addr_port_lookup can't handle (any bracketed) ipv6 part either. it's impossible to request IPv6 connection without dns mafia.
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