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dnsmgr.c: dnsmgr_refresh() incorrectly flags change with DNS round-robin

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The dnsmgr_refresh() function checks to see if the IP address associated
with a name/service has changed. The gotcha is that the ast_get_ip_or_srv()
function only returns the first IP address returned by the DNS query. If
there are multiple IPs associated with the name and the returned order is
not consistent (e.g. with DNS round-robin) then the other IP addresses are
not included in the comparison and the entry is flagged as changed even
though the IP is still valid.

Updated the code to check all IP addresses and flag a change only if the
original IP is no longer valid.

Resolves: #924
This commit is contained in:
Allan Nathanson
2024-09-29 18:45:51 -04:00
parent 00d72b0e9e
commit 4a3319a587
3 changed files with 55 additions and 11 deletions
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37
main/acl.c
View File

@@ -872,18 +872,29 @@ enum ast_acl_sense ast_apply_ha(const struct ast_ha *ha, const struct ast_sockad
return res;
}
static int resolve_first(struct ast_sockaddr *addr, const char *name, int flag,
int family)
static int resolve_match_or_first(struct ast_sockaddr *addr, const char *name, int flag,
int family, struct ast_sockaddr *preference)
{
struct ast_sockaddr *addrs;
int addrs_cnt;
addrs_cnt = ast_sockaddr_resolve(&addrs, name, flag, family);
if (addrs_cnt > 0) {
if (addrs_cnt > 1) {
struct ast_sockaddr *resolved = &addrs[0];
if (preference) {
int i;
for (i = 0; i < addrs_cnt; i++) {
if (!ast_sockaddr_cmp_addr(preference, &addrs[i])) {
resolved = &addrs[i];
break;
}
}
} else if (addrs_cnt > 1) {
ast_debug(1, "Multiple addresses. Using the first only\n");
}
ast_sockaddr_copy(addr, &addrs[0]);
ast_sockaddr_copy(addr, resolved);
ast_free(addrs);
} else {
ast_log(LOG_WARNING, "Unable to lookup '%s'\n", name);
@@ -893,7 +904,8 @@ static int resolve_first(struct ast_sockaddr *addr, const char *name, int flag,
return 0;
}
int ast_get_ip_or_srv(struct ast_sockaddr *addr, const char *hostname, const char *service)
int ast_get_ip_or_srv_with_preference(struct ast_sockaddr *addr, const char *hostname,
const char *service, struct ast_sockaddr *preference)
{
char srv[256];
char host[256];
@@ -907,7 +919,7 @@ int ast_get_ip_or_srv(struct ast_sockaddr *addr, const char *hostname, const cha
}
}
if (resolve_first(addr, hostname, PARSE_PORT_FORBID, addr->ss.ss_family) != 0) {
if (resolve_match_or_first(addr, hostname, PARSE_PORT_FORBID, addr->ss.ss_family, preference) != 0) {
return -1;
}
@@ -918,6 +930,11 @@ int ast_get_ip_or_srv(struct ast_sockaddr *addr, const char *hostname, const cha
return 0;
}
int ast_get_ip_or_srv(struct ast_sockaddr *addr, const char *hostname, const char *service)
{
return ast_get_ip_or_srv_with_preference(addr, hostname, service, NULL);
}
struct dscp_codepoint {
char *name;
unsigned int space;
@@ -1064,17 +1081,17 @@ int ast_find_ourip(struct ast_sockaddr *ourip, const struct ast_sockaddr *bindad
if (gethostname(ourhost, sizeof(ourhost) - 1)) {
ast_log(LOG_WARNING, "Unable to get hostname\n");
} else {
if (resolve_first(ourip, ourhost, PARSE_PORT_FORBID, family) == 0) {
/* reset port since resolve_first wipes this out */
if (resolve_match_or_first(ourip, ourhost, PARSE_PORT_FORBID, family, NULL) == 0) {
/* reset port since resolve_match_or_first wipes this out */
ast_sockaddr_set_port(ourip, port);
return 0;
}
}
ast_debug(3, "Trying to check A.ROOT-SERVERS.NET and get our IP address for that connection\n");
/* A.ROOT-SERVERS.NET. */
if (!resolve_first(&root, "A.ROOT-SERVERS.NET", PARSE_PORT_FORBID, 0) &&
if (!resolve_match_or_first(&root, "A.ROOT-SERVERS.NET", PARSE_PORT_FORBID, 0, NULL) &&
!ast_ouraddrfor(&root, ourip)) {
/* reset port since resolve_first wipes this out */
/* reset port since resolve_match_or_first wipes this out */
ast_sockaddr_set_port(ourip, port);
return 0;
}

2
main/dnsmgr.c
View File

@@ -211,7 +211,7 @@ static int dnsmgr_refresh(struct ast_dnsmgr_entry *entry, int verbose)
ast_debug(6, "refreshing '%s'\n", entry->name);
tmp.ss.ss_family = entry->family;
if (!ast_get_ip_or_srv(&tmp, entry->name, entry->service)) {
if (!ast_get_ip_or_srv_with_preference(&tmp, entry->name, entry->service, entry->result)) {
if (!ast_sockaddr_port(&tmp)) {
ast_sockaddr_set_port(&tmp, ast_sockaddr_port(entry->result));
}