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352f4ff9 | 1 | /* Temporary, thread-local resolver state. |
04277e02 | 2 | Copyright (C) 2017-2019 Free Software Foundation, Inc. |
352f4ff9 FW |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, see | |
17 | <http://www.gnu.org/licenses/>. */ | |
18 | ||
19 | /* struct resolv_context objects are allocated on the heap, | |
20 | initialized by __resolv_context_get (and its variants), and | |
21 | destroyed by __resolv_context_put. | |
22 | ||
23 | A nested call to __resolv_context_get (after another call to | |
24 | __resolv_context_get without a matching __resolv_context_put call, | |
25 | on the same thread) returns the original pointer, instead of | |
26 | allocating a new context. This prevents unexpected reloading of | |
27 | the resolver configuration. Care is taken to keep the context in | |
28 | sync with the thread-local _res object. (This does not happen with | |
3f8b44be | 29 | __resolv_context_get_override.) |
352f4ff9 FW |
30 | |
31 | In contrast to struct __res_state, struct resolv_context is not | |
32 | affected by ABI compatibility concerns. | |
33 | ||
34 | For the benefit of the res_n* functions, a struct __res_state | |
35 | pointer is included in the context object, and a separate | |
36 | initialization function is provided. */ | |
37 | ||
38 | #ifndef _RESOLV_CONTEXT_H | |
39 | #define _RESOLV_CONTEXT_H | |
40 | ||
f30a54b2 FW |
41 | #include <bits/types/res_state.h> |
42 | #include <resolv/resolv_conf.h> | |
352f4ff9 FW |
43 | #include <stdbool.h> |
44 | #include <stddef.h> | |
352f4ff9 FW |
45 | |
46 | /* Temporary resolver state. */ | |
47 | struct resolv_context | |
48 | { | |
49 | struct __res_state *resp; /* Backing resolver state. */ | |
50 | ||
f30a54b2 FW |
51 | /* Extended resolver state. This is set to NULL if the |
52 | __resolv_context_get functions are unable to locate an associated | |
53 | extended state. In this case, the configuration data in *resp | |
54 | has to be used; otherwise, the data from *conf should be | |
55 | preferred (because it is a superset). */ | |
56 | struct resolv_conf *conf; | |
352f4ff9 FW |
57 | |
58 | /* The following fields are for internal use within the | |
59 | resolv_context module. */ | |
60 | size_t __refcount; /* Count of reusages by the get functions. */ | |
61 | bool __from_res; /* True if created from _res. */ | |
62 | ||
3f8b44be FW |
63 | /* Single-linked list of resolver contexts. Used for memory |
64 | deallocation on thread cancellation. */ | |
352f4ff9 FW |
65 | struct resolv_context *__next; |
66 | }; | |
67 | ||
68 | /* Return the current temporary resolver context, or NULL if there was | |
69 | an error (indicated by errno). A call to this function must be | |
70 | paired with a call to __resolv_context_put. */ | |
71 | struct resolv_context *__resolv_context_get (void) | |
72 | __attribute__ ((warn_unused_result)); | |
73 | libc_hidden_proto (__resolv_context_get) | |
74 | ||
75 | /* Deallocate the temporary resolver context. Converse of | |
3f8b44be | 76 | __resolv_context_get. Do nothing if CTX is NULL. */ |
352f4ff9 FW |
77 | void __resolv_context_put (struct resolv_context *ctx); |
78 | libc_hidden_proto (__resolv_context_put) | |
79 | ||
80 | /* Like __resolv_context_get, but the _res structure can be partially | |
81 | initialzed and those changes will not be overwritten. */ | |
82 | struct resolv_context *__resolv_context_get_preinit (void) | |
83 | __attribute__ ((warn_unused_result)); | |
84 | libc_hidden_proto (__resolv_context_get_preinit) | |
85 | ||
86 | /* Wrap a struct __res_state object in a struct resolv_context object. | |
87 | A call to this function must be paired with a call to | |
88 | __resolv_context_put. */ | |
89 | struct resolv_context *__resolv_context_get_override (struct __res_state *) | |
90 | __attribute__ ((nonnull (1), warn_unused_result)); | |
91 | libc_hidden_proto (__resolv_context_get_override) | |
92 | ||
3f853f22 FW |
93 | /* Return the search path entry at INDEX, or NULL if there are fewer |
94 | than INDEX entries. */ | |
95 | static __attribute__ ((nonnull (1), unused)) const char * | |
96 | __resolv_context_search_list (const struct resolv_context *ctx, size_t index) | |
97 | { | |
98 | if (ctx->conf != NULL) | |
99 | { | |
100 | if (index < ctx->conf->search_list_size) | |
101 | return ctx->conf->search_list[index]; | |
102 | else | |
103 | return NULL; | |
104 | } | |
105 | /* Fallback. ctx->resp->dnsrch is a NULL-terminated array. */ | |
106 | for (size_t i = 0; ctx->resp->dnsrch[i] != NULL && i < MAXDNSRCH; ++i) | |
107 | if (i == index) | |
108 | return ctx->resp->dnsrch[i]; | |
109 | return NULL; | |
110 | } | |
111 | ||
a1c4eb87 FW |
112 | /* Return the number of name servers. */ |
113 | static __attribute__ ((nonnull (1), unused)) size_t | |
114 | __resolv_context_nameserver_count (const struct resolv_context *ctx) | |
115 | { | |
116 | if (ctx->conf != NULL) | |
117 | return ctx->conf->nameserver_list_size; | |
118 | else | |
119 | return ctx->resp->nscount; | |
120 | } | |
121 | ||
122 | /* Return a pointer to the socket address of the name server INDEX, or | |
123 | NULL if the index is out of bounds. */ | |
124 | static __attribute__ ((nonnull (1), unused)) const struct sockaddr * | |
125 | __resolv_context_nameserver (const struct resolv_context *ctx, size_t index) | |
126 | { | |
127 | if (ctx->conf != NULL) | |
128 | { | |
129 | if (index < ctx->conf->nameserver_list_size) | |
130 | return ctx->conf->nameserver_list[index]; | |
131 | } | |
132 | else | |
133 | if (index < ctx->resp->nscount) | |
134 | { | |
135 | if (ctx->resp->nsaddr_list[index].sin_family != 0) | |
136 | return (const struct sockaddr *) &ctx->resp->nsaddr_list[index]; | |
137 | else | |
138 | return (const struct sockaddr *) &ctx->resp->_u._ext.nsaddrs[index]; | |
139 | } | |
140 | return NULL; | |
141 | } | |
142 | ||
143 | /* Return the number of sort list entries. */ | |
144 | static __attribute__ ((nonnull (1), unused)) size_t | |
145 | __resolv_context_sort_count (const struct resolv_context *ctx) | |
146 | { | |
147 | if (ctx->conf != NULL) | |
148 | return ctx->conf->sort_list_size; | |
149 | else | |
150 | return ctx->resp->nsort; | |
151 | } | |
152 | ||
153 | /* Return the sort list entry at INDEX. */ | |
154 | static __attribute__ ((nonnull (1), unused)) struct resolv_sortlist_entry | |
155 | __resolv_context_sort_entry (const struct resolv_context *ctx, size_t index) | |
156 | { | |
157 | if (ctx->conf != NULL) | |
158 | { | |
159 | if (index < ctx->conf->sort_list_size) | |
160 | return ctx->conf->sort_list[index]; | |
161 | /* Fall through. */ | |
162 | } | |
163 | else if (index < ctx->resp->nsort) | |
164 | return (struct resolv_sortlist_entry) | |
165 | { | |
166 | .addr = ctx->resp->sort_list[index].addr, | |
167 | .mask = ctx->resp->sort_list[index].mask, | |
168 | }; | |
169 | ||
170 | return (struct resolv_sortlist_entry) { .mask = 0, }; | |
171 | } | |
172 | ||
352f4ff9 FW |
173 | /* Called during thread shutdown to free the associated resolver |
174 | context (mostly in response to cancellation, otherwise the | |
175 | __resolv_context_get/__resolv_context_put pairing will already have | |
176 | deallocated the context object). */ | |
177 | void __resolv_context_freeres (void) attribute_hidden; | |
178 | ||
179 | #endif /* _RESOLV_CONTEXT_H */ |