When parsing a resolv.conf file that has "search .", parseResolvConf should
accept the "." entry verbatim. Before this commit, parseResolvConf
unconditionally trimmed the "." suffix, which in the case of "." resulted
in a "" entry (that is, the empty string). This empty entry could lead
parseResolvConf to produce a resolv.conf file with "search ". Resolvers
could fail to parse such a resolv.conf file from parseResolvConf, thus
breaking DNS resolution in pods. After this commit, parseResolvConf
accepts a resolv.conf file with "search ." and passes the "." entry through
verbatim to produce a valid resolv.conf file. The "." suffix is still
trimmed for any entry that does not solely comprise ".".
Follow-up to commit a215a88d91.
* pkg/kubelet/network/dns/dns.go (parseResolvConf): Handle a "." entry in
the search path by copying it verbatim.
* pkg/kubelet/network/dns/dns_test.go (TestParseResolvConf): Add a test
case for "search .".
5832b84200