DRAFT: Factor gen_host46_byname() out. #1519
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The function needs to translate a [well-formed] IPv6 address string to a struct in6_addr. Although pcap_nametoaddrinfo() in fact does that, it overshoots the problem space unnecessarily and requires managing of the associated freeaddrinfo() call. Also the "resolved to multiple address" condition is never true because in this case the string is an address, not a hostname, and cannot translate to more than one binary address. Switch to inet_pton(), which fits the problem space much better, and verify that it has not failed (very unlikely, but still).
In gen_scode() case Q_GATEWAY delegate the remaining memory management and error handling away; now if gen_gateway() returns, it always returns a non-NULL value. In gen_gateway() handle all errors as early as possible; instead of testing whether ai_addr is NULL test whether ai_family is set to the AF of interest, when that's the case, ai_addr is not NULL (this is how gen_scode() implements case Q_HOST).
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This is the more difficult part of a prototype I started, but could not quickly complete earlier. The intent is simple: since
gateway Xnominally includesnot host X, and since bothgen_gateway()andgen_scode()callpcap_addrinfo()and process the result(s) in a very similar manner, having a slightly different code block in each function makes the code harder to maintain. However, the complexity turned out to be in the detail (including #1512), so this work-in-progress revision fails many tests. Also before this can be progressed any further, the reject filter tests must cover all code paths that go throughpcap_addrinfo()and fail to resolve the hostname.