Exercising the connect fallback needs a host that resolves to a dead address
first and a live one next, deterministically and offline. A true SYN
black-hole can't be simulated without root, but a refused address can.
HTTRACK_DEBUG_RESOLVE="host:ip[,ip...]" pins a host's resolution to a fixed
address list (curl --resolve style), reusing the PR1 resolver seam: an
addrinfo backend that synthesizes the listed addresses for the named host and
delegates other hosts to libc (copying into its own allocations so one
freeaddrinfo frees both). It is a debug/test hook, inert unless the env var is
set, and IPv6-build-only like the rest of the resolver list.
The new local crawl test binds the server to 127.0.0.1 and resolves a host to
127.0.0.2 (refused) then 127.0.0.1: the mirror only succeeds via the fallback.
A V6_SUPPORT substitution (mirroring HTTPS_SUPPORT) lets it skip on non-IPv6
builds.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>
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