Reinforce DNS reverse resolution test #3113
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It's not my localhost problem, github CI also suffers. The branch that changes nothing, and the CI job on it that fails |
tests/unit/dns_test.cc
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| hostent e = co_await d.get_host_by_name(seastar_name, inet_address::family::INET); | ||
| hostent a = co_await d.get_host_by_addr(e.addr_list.front()); | ||
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| try_again: |
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Suggest:
while (!hostnames.empty()) {
try {
auto d = ...;
break;
} catch(...)
...
continue;
}
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OK, reimplemented with a for-loop
Signed-off-by: Pavel Emelyanov <[email protected]>
In case reverse resolution fails, try again with another host name. At least one of them should succeed. Signed-off-by: Pavel Emelyanov <[email protected]>
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upd:
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It might be a good idea to use these domains: $ dig +short one.one.one.one
1.0.0.1
1.1.1.1
$ dig +short dns.google
8.8.4.4
8.8.8.8
$ dig +short localhost
127.0.0.1 |
| hostent a = co_await d.get_host_by_addr(e.addr_list.front()); | ||
| hostent e2 = co_await d.get_host_by_name(a.names.front(), inet_address::family::INET); | ||
| BOOST_REQUIRE(std::count(e2.addr_list.begin(), e2.addr_list.end(), e.addr_list.front())); | ||
| co_await d.close(); |
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This is not an accurate translation, we lose d.close() on exception. And since you do expect failures, we shouldn't leak here.
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Failures that are "expected" don't lose close -- the d is created once before loop, and in case loop continues it re-uses that single resolver. Exceptions that are not caught make test fail anyway
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IMO, a better approach is to set up local dns with dnsmasq as a fixture so we have reliable infrastructure. But I don't known if it's worth the effort. |
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The test does three resolutions in a row -- hostname to address, then address to hostname and finally the reverse-resolved name back to address. The last list of IP-s is checked to contain front IP from the first list. The piggy host for the fun is seastar.io.
Sometimes, reverse resolution fails. E.g. 2b51022 changed the name from www.google.com to seastar.io with the explanation that google hostname's address cannot be resolved back. Now it happened with seastar.io (and www.google.com healed back). The proposal is to try several hostnames in a row, and tolerate the reverse lookup failure.