diff options
author | russell <russell@f38db490-d61c-443f-a65b-d21fe96a405b> | 2008-01-19 00:19:29 +0000 |
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committer | russell <russell@f38db490-d61c-443f-a65b-d21fe96a405b> | 2008-01-19 00:19:29 +0000 |
commit | f8247040e6231c4b3b5099ea3a526348b7941566 (patch) | |
tree | 0cc92ad6ebf6ae49a62f6e7ef8ec819121d63630 /trunk/main/srv.c | |
parent | d88e56c61ce2042544c1a8a71c93b69ab2e6ffba (diff) |
Creating tag for the release of asterisk-1.6.0-beta1v1.6.0-beta1
git-svn-id: http://svn.digium.com/svn/asterisk/tags/1.6.0-beta1@99163 f38db490-d61c-443f-a65b-d21fe96a405b
Diffstat (limited to 'trunk/main/srv.c')
-rw-r--r-- | trunk/main/srv.c | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/trunk/main/srv.c b/trunk/main/srv.c new file mode 100644 index 000000000..3950e255f --- /dev/null +++ b/trunk/main/srv.c @@ -0,0 +1,238 @@ +/* + * Asterisk -- An open source telephony toolkit. + * + * Copyright (C) 1999 - 2005, Digium, Inc. + * + * Mark Spencer <markster@digium.com> + * + * Funding provided by nic.at + * + * See http://www.asterisk.org for more information about + * the Asterisk project. Please do not directly contact + * any of the maintainers of this project for assistance; + * the project provides a web site, mailing lists and IRC + * channels for your use. + * + * This program is free software, distributed under the terms of + * the GNU General Public License Version 2. See the LICENSE file + * at the top of the source tree. + */ + +/*! \file + * + * \brief DNS SRV Record Lookup Support for Asterisk + * + * \author Mark Spencer <markster@digium.com> + * + * \arg See also \ref AstENUM + * + * \note Funding provided by nic.at + */ + +#include "asterisk.h" + +ASTERISK_FILE_VERSION(__FILE__, "$Revision$") + +#include <netinet/in.h> +#include <arpa/nameser.h> +#ifdef __APPLE__ +#if __APPLE_CC__ >= 1495 +#include <arpa/nameser_compat.h> +#endif +#endif +#include <resolv.h> + +#include "asterisk/channel.h" +#include "asterisk/srv.h" +#include "asterisk/dns.h" +#include "asterisk/utils.h" +#include "asterisk/linkedlists.h" + +#ifdef __APPLE__ +#undef T_SRV +#define T_SRV 33 +#endif + +struct srv_entry { + unsigned short priority; + unsigned short weight; + unsigned short port; + unsigned int weight_sum; + AST_LIST_ENTRY(srv_entry) list; + char host[1]; +}; + +struct srv_context { + unsigned int have_weights:1; + AST_LIST_HEAD_NOLOCK(srv_entries, srv_entry) entries; +}; + +static int parse_srv(unsigned char *answer, int len, unsigned char *msg, struct srv_entry **result) +{ + struct srv { + unsigned short priority; + unsigned short weight; + unsigned short port; + } __attribute__ ((__packed__)) *srv = (struct srv *) answer; + + int res = 0; + char repl[256] = ""; + struct srv_entry *entry; + + if (len < sizeof(*srv)) + return -1; + + answer += sizeof(*srv); + len -= sizeof(*srv); + + if ((res = dn_expand(msg, answer + len, answer, repl, sizeof(repl) - 1)) <= 0) { + ast_log(LOG_WARNING, "Failed to expand hostname\n"); + return -1; + } + + /* the magic value "." for the target domain means that this service + is *NOT* available at the domain we searched */ + if (!strcmp(repl, ".")) + return -1; + + if (!(entry = ast_calloc(1, sizeof(*entry) + strlen(repl)))) + return -1; + + entry->priority = ntohs(srv->priority); + entry->weight = ntohs(srv->weight); + entry->port = ntohs(srv->port); + strcpy(entry->host, repl); + + *result = entry; + + return 0; +} + +static int srv_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer) +{ + struct srv_context *c = (struct srv_context *) context; + struct srv_entry *entry = NULL; + struct srv_entry *current; + + if (parse_srv(answer, len, fullanswer, &entry)) + return -1; + + if (entry->weight) + c->have_weights = 1; + + AST_LIST_TRAVERSE_SAFE_BEGIN(&c->entries, current, list) { + /* insert this entry just before the first existing + entry with a higher priority */ + if (current->priority <= entry->priority) + continue; + + AST_LIST_INSERT_BEFORE_CURRENT(entry, list); + entry = NULL; + break; + } + AST_LIST_TRAVERSE_SAFE_END; + + /* if we didn't find a place to insert the entry before an existing + entry, then just add it to the end */ + if (entry) + AST_LIST_INSERT_TAIL(&c->entries, entry, list); + + return 1; +} + +/* Do the bizarre SRV record weight-handling algorithm + involving sorting and random number generation... + + See RFC 2782 if you want know why this code does this +*/ +static void process_weights(struct srv_context *context) +{ + struct srv_entry *current; + struct srv_entries newlist = AST_LIST_HEAD_NOLOCK_INIT_VALUE; + + while (AST_LIST_FIRST(&context->entries)) { + unsigned int random_weight; + unsigned int weight_sum; + unsigned short cur_priority = AST_LIST_FIRST(&context->entries)->priority; + struct srv_entries temp_list = AST_LIST_HEAD_NOLOCK_INIT_VALUE; + weight_sum = 0; + + AST_LIST_TRAVERSE_SAFE_BEGIN(&context->entries, current, list) { + if (current->priority != cur_priority) + break; + + AST_LIST_MOVE_CURRENT(&temp_list, list); + } + AST_LIST_TRAVERSE_SAFE_END; + + while (AST_LIST_FIRST(&temp_list)) { + weight_sum = 0; + AST_LIST_TRAVERSE(&temp_list, current, list) + current->weight_sum = weight_sum += current->weight; + + /* if all the remaining entries have weight == 0, + then just append them to the result list and quit */ + if (weight_sum == 0) { + AST_LIST_APPEND_LIST(&newlist, &temp_list, list); + break; + } + + random_weight = 1 + (unsigned int) ((float) weight_sum * (ast_random() / ((float) RAND_MAX + 1.0))); + + AST_LIST_TRAVERSE_SAFE_BEGIN(&temp_list, current, list) { + if (current->weight < random_weight) + continue; + + AST_LIST_MOVE_CURRENT(&newlist, list); + break; + } + AST_LIST_TRAVERSE_SAFE_END; + } + + } + + /* now that the new list has been ordered, + put it in place */ + + AST_LIST_APPEND_LIST(&context->entries, &newlist, list); +} + +int ast_get_srv(struct ast_channel *chan, char *host, int hostlen, int *port, const char *service) +{ + struct srv_context context = { .entries = AST_LIST_HEAD_NOLOCK_INIT_VALUE }; + struct srv_entry *current; + int ret; + + if (chan && ast_autoservice_start(chan) < 0) + return -1; + + ret = ast_search_dns(&context, service, C_IN, T_SRV, srv_callback); + + if (context.have_weights) + process_weights(&context); + + if (chan) + ret |= ast_autoservice_stop(chan); + + /* TODO: there could be a "." entry in the returned list of + answers... if so, this requires special handling */ + + /* the list of entries will be sorted in the proper selection order + already, so we just need the first one (if any) */ + + if ((ret > 0) && (current = AST_LIST_REMOVE_HEAD(&context.entries, list))) { + ast_copy_string(host, current->host, hostlen); + *port = current->port; + ast_free(current); + ast_verb(3, "ast_get_srv: SRV lookup for '%s' mapped to host %s, port %d\n", + service, host, *port); + } else { + host[0] = '\0'; + *port = -1; + } + + while ((current = AST_LIST_REMOVE_HEAD(&context.entries, list))) + ast_free(current); + + return ret; +} |