| /* Temporary, thread-local resolver state. |
| Copyright (C) 2017-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| /* struct resolv_context objects are allocated on the heap, |
| initialized by __resolv_context_get (and its variants), and |
| destroyed by __resolv_context_put. |
| |
| A nested call to __resolv_context_get (after another call to |
| __resolv_context_get without a matching __resolv_context_put call, |
| on the same thread) returns the original pointer, instead of |
| allocating a new context. This prevents unexpected reloading of |
| the resolver configuration. Care is taken to keep the context in |
| sync with the thread-local _res object. (This does not happen with |
| __resolv_context_get_override, and __resolv_context_get_no_inet6 may |
| also interpose another context object if RES_USE_INET6 needs to be |
| disabled.) |
| |
| In contrast to struct __res_state, struct resolv_context is not |
| affected by ABI compatibility concerns. |
| |
| For the benefit of the res_n* functions, a struct __res_state |
| pointer is included in the context object, and a separate |
| initialization function is provided. */ |
| |
| #ifndef _RESOLV_CONTEXT_H |
| #define _RESOLV_CONTEXT_H |
| |
| #include <bits/types/res_state.h> |
| #include <resolv/resolv_conf.h> |
| #include <stdbool.h> |
| #include <stddef.h> |
| |
| /* Temporary resolver state. */ |
| struct resolv_context |
| { |
| struct __res_state *resp; /* Backing resolver state. */ |
| |
| /* Extended resolver state. This is set to NULL if the |
| __resolv_context_get functions are unable to locate an associated |
| extended state. In this case, the configuration data in *resp |
| has to be used; otherwise, the data from *conf should be |
| preferred (because it is a superset). */ |
| struct resolv_conf *conf; |
| |
| /* The following fields are for internal use within the |
| resolv_context module. */ |
| size_t __refcount; /* Count of reusages by the get functions. */ |
| bool __from_res; /* True if created from _res. */ |
| |
| /* If RES_USE_INET6 was disabled at this level, this field points to |
| the previous context. */ |
| struct resolv_context *__next; |
| }; |
| |
| /* Return the current temporary resolver context, or NULL if there was |
| an error (indicated by errno). A call to this function must be |
| paired with a call to __resolv_context_put. */ |
| struct resolv_context *__resolv_context_get (void) |
| __attribute__ ((warn_unused_result)); |
| libc_hidden_proto (__resolv_context_get) |
| |
| /* Deallocate the temporary resolver context. Converse of |
| __resolv_context_get. Restore the RES_USE_INET6 flag if necessary. |
| Do nothing if CTX is NULL. */ |
| void __resolv_context_put (struct resolv_context *ctx); |
| libc_hidden_proto (__resolv_context_put) |
| |
| /* Like __resolv_context_get, but the _res structure can be partially |
| initialzed and those changes will not be overwritten. */ |
| struct resolv_context *__resolv_context_get_preinit (void) |
| __attribute__ ((warn_unused_result)); |
| libc_hidden_proto (__resolv_context_get_preinit) |
| |
| /* Wrap a struct __res_state object in a struct resolv_context object. |
| A call to this function must be paired with a call to |
| __resolv_context_put. */ |
| struct resolv_context *__resolv_context_get_override (struct __res_state *) |
| __attribute__ ((nonnull (1), warn_unused_result)); |
| libc_hidden_proto (__resolv_context_get_override) |
| |
| /* Return the search path entry at INDEX, or NULL if there are fewer |
| than INDEX entries. */ |
| static __attribute__ ((nonnull (1), unused)) const char * |
| __resolv_context_search_list (const struct resolv_context *ctx, size_t index) |
| { |
| if (ctx->conf != NULL) |
| { |
| if (index < ctx->conf->search_list_size) |
| return ctx->conf->search_list[index]; |
| else |
| return NULL; |
| } |
| /* Fallback. ctx->resp->dnsrch is a NULL-terminated array. */ |
| for (size_t i = 0; ctx->resp->dnsrch[i] != NULL && i < MAXDNSRCH; ++i) |
| if (i == index) |
| return ctx->resp->dnsrch[i]; |
| return NULL; |
| } |
| |
| /* Return the number of name servers. */ |
| static __attribute__ ((nonnull (1), unused)) size_t |
| __resolv_context_nameserver_count (const struct resolv_context *ctx) |
| { |
| if (ctx->conf != NULL) |
| return ctx->conf->nameserver_list_size; |
| else |
| return ctx->resp->nscount; |
| } |
| |
| /* Return a pointer to the socket address of the name server INDEX, or |
| NULL if the index is out of bounds. */ |
| static __attribute__ ((nonnull (1), unused)) const struct sockaddr * |
| __resolv_context_nameserver (const struct resolv_context *ctx, size_t index) |
| { |
| if (ctx->conf != NULL) |
| { |
| if (index < ctx->conf->nameserver_list_size) |
| return ctx->conf->nameserver_list[index]; |
| } |
| else |
| if (index < ctx->resp->nscount) |
| { |
| if (ctx->resp->nsaddr_list[index].sin_family != 0) |
| return (const struct sockaddr *) &ctx->resp->nsaddr_list[index]; |
| else |
| return (const struct sockaddr *) &ctx->resp->_u._ext.nsaddrs[index]; |
| } |
| return NULL; |
| } |
| |
| /* Return the number of sort list entries. */ |
| static __attribute__ ((nonnull (1), unused)) size_t |
| __resolv_context_sort_count (const struct resolv_context *ctx) |
| { |
| if (ctx->conf != NULL) |
| return ctx->conf->sort_list_size; |
| else |
| return ctx->resp->nsort; |
| } |
| |
| /* Return the sort list entry at INDEX. */ |
| static __attribute__ ((nonnull (1), unused)) struct resolv_sortlist_entry |
| __resolv_context_sort_entry (const struct resolv_context *ctx, size_t index) |
| { |
| if (ctx->conf != NULL) |
| { |
| if (index < ctx->conf->sort_list_size) |
| return ctx->conf->sort_list[index]; |
| /* Fall through. */ |
| } |
| else if (index < ctx->resp->nsort) |
| return (struct resolv_sortlist_entry) |
| { |
| .addr = ctx->resp->sort_list[index].addr, |
| .mask = ctx->resp->sort_list[index].mask, |
| }; |
| |
| return (struct resolv_sortlist_entry) { .mask = 0, }; |
| } |
| |
| /* Called during thread shutdown to free the associated resolver |
| context (mostly in response to cancellation, otherwise the |
| __resolv_context_get/__resolv_context_put pairing will already have |
| deallocated the context object). */ |
| void __resolv_context_freeres (void) attribute_hidden; |
| |
| #endif /* _RESOLV_CONTEXT_H */ |