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path: root/src/network/lookup_name.c
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2016-01-28reuse parsed resolv.conf in dns core to avoid re-reading/re-parsingRich Felker-5/+6
2016-01-28add support for search domains to dns resolverRich Felker-1/+41
search is only performed if the search or domain keyword is used in resolv.conf and the queried name has fewer than ndots dots. there is no default domain and names with >=ndots dots are never subjected to search; failure in the root scope is final. the (non-POSIX) res_search API presently does not honor search. this may be added at some point in the future if needed. resolv.conf is now parsed twice, at two different layers of the code involved. this will be fixed in a subsequent patch.
2016-01-28fix handling of dns response codesRich Felker-1/+2
rcode of 3 (NxDomain) was treated as a hard EAI_NONAME failure, but it should instead return 0 (no results) so the caller can continue searching. this will be important for adding search domain support. the top-level caller will automatically return EAI_NONAME if there are zero results at the end. also, the case where rcode is 0 (success) but there are no results was not handled. this happens when the domain exists but there are no A or AAAA records for it. in this case a hard EAI_NONAME should be imposed to inhibit further search, since the name was defined and just does not have any address associated with it. previously a misleading hard failure of EAI_FAIL was reported.
2015-10-26safely handle failure to open hosts, services, resolv.conf filesRich Felker-1/+9
previously, transient failures like fd exhaustion or other resource-related errors were treated the same as non-existence of these files, leading to fallbacks or false-negative results. in particular: - failure to open hosts resulted in fallback to dns, possibly yielding EAI_NONAME for a hostname that should be defined locally, or an unwanted result from dns that the hosts file was intended to replace. - failure to open services resulted in EAI_SERVICE. - failure to open resolv.conf resulted in querying localhost rather than the configured nameservers. now, only permanent errors trigger the fallback behaviors above; all other errors are reportable to the caller as EAI_SYSTEM.
2014-06-21implement result address sorting in the resolver (getaddrinfo, etc.)Rich Felker-0/+135
2014-06-06accept trailing . and empty domain namesSzabolcs Nagy-3/+4
trailing . should be accepted in domain name strings by convention (RFC 1034), host name lookup accepts "." but rejects empty "", res_* interfaces also accept empty name following existing practice.
2014-06-05fix the domain name length limit checksSzabolcs Nagy-2/+2
A domain name is at most 255 bytes long (RFC 1035), but the string representation is two bytes smaller so the strlen maximum is 253.
2014-06-04add support for reverse name lookups from hosts file to getnameinfoRich Felker-38/+3
this also affects the legacy gethostbyaddr family, which uses getnameinfo as its backend. some other minor changes associated with the refactoring of source files are also made; in particular, the resolv.conf parser now uses the same code that's used elsewhere to handle ip literals, so as a side effect it can now accept a scope id for nameserver addressed with link-local scope.
2014-06-04add support for ipv6 scope_id to getaddrinfo and getnameinfoRich Felker-4/+27
for all address types, a scope_id specified as a decimal value is accepted. for addresses with link-local scope, a string containing the interface name is also accepted. some changes are made to error handling to avoid unwanted fallbacks in the case where the scope_id is invalid: if an earlier name lookup backend fails with an error rather than simply "0 results", this failure now suppresses any later attempts with other backends. in getnameinfo, a light "itoa" type function is added for generating decimal scope_id results, and decimal port strings for services are also generated using this function now so as not to pull in the dependency on snprintf. in netdb.h, a definition for the NI_NUMERICSCOPE flag is added. this is required by POSIX (it was previously missing) and needed to allow callers to suppress interface-name lookups.
2014-06-03fix negative response and non-response handling for dns queriesRich Felker-1/+4
previously, all failures to obtain at least one address were treated as nonexistant names (EAI_NONAME). this failed to account for the possibility of transient failures (no response at all, or a response with rcode of 2, server failure) or permanent failures that do not indicate the nonexistence of the requested name. only an rcode of 3 should be treated as an indication of nonexistence.
2014-06-02remove cruft from old resolver and numeric ip parsingRich Felker-1/+3
the old resolver code used a function __ipparse which contained the logic for inet_addr and inet_aton, which is needed in getaddrinfo. this was phased out in the resolver overhaul in favor of directly using inet_aton and inet_pton as appropriate. this commit cleans up some stuff that was left behind.
2014-06-02switch standard resolver functions to use the new dns backendRich Felker-21/+61
this is the third phase of the "resolver overhaul" project. this commit removes all of the old dns code, and switches the __lookup_name backend (used by getaddrinfo, etc.) and the getnameinfo function to use the newly implemented __res_mkquery and __res_msend interfaces. for parsing the results, a new callback-based __dns_parse function, based on __dns_get_rr from the old dns code, is used.
2014-06-02fix off-by-one in checking hostname length in new resolver backendRich Felker-2/+2
this bug was introduced in the recent resolver overhaul commits. it likely had visible symptoms. these were probably limited to wrongly accepting truncated versions of over-long names (vs rejecting them), as opposed to stack-based overflows or anything more severe, but no extensive checks were made. there have been no releases where this bug was present.
2014-05-31refactor getaddrinfo and add support for most remaining featuresRich Felker-0/+168
this is the first phase of the "resolver overhaul" project. conceptually, the results of getaddrinfo are a direct product of a list of address results and a list of service results. the new code makes this explicit by computing these lists separately and combining the results. this adds support for services that have both tcp and udp versions, where the caller has not specified which it wants, and eliminates a number of duplicate code paths which were all producing the final output addrinfo structures, but in subtly different ways, making it difficult to implement any of the features which were missing. in addition to the above benefits, the refactoring allows for legacy functions like gethostbyname to be implemented without using the getaddrinfo function itself. such changes to the legacy functions have not yet been made, however. further improvements include matching of service alias names from /etc/services (previously only the primary name was supported), returning multiple results from /etc/hosts (previously only the first matching line was honored), and support for the AI_V4MAPPED and AI_ALL flags. features which remain unimplemented are IDN translations (encoding non-ASCII hostnames for DNS lookup) and the AI_ADDRCONFIG flag. at this point, the DNS-based name resolving code is still based on the old interfaces in __dns.c, albeit somewhat simpler in its use of them. there may be some dead code which could already be removed, but changes to this layer will be a later phase of the resolver overhaul.