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net: sockets: Make sure that getaddrinfo() cannot hang forever 

If for some reason the DNS resolver callback is not called properly
then make sure that semaphore will not block forever.

Fixes #15197

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
This commit is contained in:
Jukka Rissanen 2019-04-05 15:00:55 +03:00 committed by Anas Nashif
parent 22c9646b97
commit 1897896e97
2 changed files with 43 additions and 32 deletions
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10
subsys/net/lib/sockets/Kconfig
View File

@ -29,6 +29,16 @@ config NET_SOCKETS_POLL_MAX
help
Maximum number of entries supported for poll() call.
config NET_SOCKETS_DNS_TIMEOUT
int "Timeout value in milliseconds for DNS queries"
default 2000
range 1000 300000
depends on DNS_RESOLVER
help
This variable specifies time in milliseconds after which DNS
query is considered timeout. Minimum timeout is 1 second and
maximum timeout is 5 min.
config NET_SOCKETS_SOCKOPT_TLS
bool "Enable TCP TLS socket option support [EXPERIMENTAL]"
select TLS_CREDENTIALS

65
subsys/net/lib/sockets/getaddrinfo.c
View File

@ -79,6 +79,19 @@ static void dns_resolve_cb(enum dns_resolve_status status,
state->idx++;
}
static int exec_query(const char *host, int family,
struct getaddrinfo_state *ai_state)
{
enum dns_query_type qtype = DNS_QUERY_TYPE_A;
if (IS_ENABLED(CONFIG_NET_IPV6) && family != AF_INET) {
qtype = DNS_QUERY_TYPE_AAAA;
}
return dns_get_addr_info(host, qtype, NULL,
dns_resolve_cb, ai_state,
CONFIG_NET_SOCKETS_DNS_TIMEOUT);
}
int z_impl_z_zsock_getaddrinfo_internal(const char *host, const char *service,
const struct zsock_addrinfo *hints,
@ -111,43 +124,31 @@ int z_impl_z_zsock_getaddrinfo_internal(const char *host, const char *service,
/* Link entries in advance */
ai_state.ai_arr[0].ai_next = &ai_state.ai_arr[1];
/* Execute if AF_UNSPEC or AF_INET4 */
if (family != AF_INET6) {
ret = dns_get_addr_info(host, DNS_QUERY_TYPE_A, NULL,
dns_resolve_cb, &ai_state, 1000);
if (ret == 0) {
k_sem_take(&ai_state.sem, K_FOREVER);
st1 = ai_state.status;
} else {
errno = -ret;
st1 = DNS_EAI_SYSTEM;
ret = exec_query(host, family, &ai_state);
if (ret == 0) {
/* If the DNS query for reason fails so that the
* dns_resolve_cb() would not be called, then we want the
* semaphore to timeout so that we will not hang forever.
* So make the sem timeout longer than the DNS timeout so that
* we do not need to start to cancel any pending DNS queries.
*/
int ret = k_sem_take(&ai_state.sem,
CONFIG_NET_SOCKETS_DNS_TIMEOUT +
K_MSEC(100));
if (ret == -EAGAIN) {
return DNS_EAI_AGAIN;
}
if (ai_state.idx > 0) {
ai_addr = &ai_state.ai_arr[ai_state.idx - 1]._ai_addr;
net_sin(ai_addr)->sin_port = htons(port);
}
st1 = ai_state.status;
} else {
errno = -ret;
st1 = DNS_EAI_SYSTEM;
}
#if defined(CONFIG_NET_IPV6)
/* Execute if AF_UNSPEC or AF_INET6 */
if (family != AF_INET) {
ret = dns_get_addr_info(host, DNS_QUERY_TYPE_AAAA, NULL,
dns_resolve_cb, &ai_state, 1000);
if (ret == 0) {
k_sem_take(&ai_state.sem, K_FOREVER);
st2 = ai_state.status;
} else {
errno = -ret;
st2 = DNS_EAI_SYSTEM;
}
if (ai_state.idx > 0) {
ai_addr = &ai_state.ai_arr[ai_state.idx - 1]._ai_addr;
net_sin6(ai_addr)->sin6_port = htons(port);
}
if (ai_state.idx > 0) {
ai_addr = &ai_state.ai_arr[ai_state.idx - 1]._ai_addr;
net_sin(ai_addr)->sin_port = htons(port);
}
#endif
/* If both attempts failed, it's error */
if (st1 && st2) {