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lib: addns: Add code for asynchronously looking up A records.

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Returns an array of struct samba_sockaddr.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
This commit is contained in:
Jeremy Allison 2020-07-17 14:21:09 -07:00 committed by Andreas Schneider
parent fc83b47051
commit 47c1b87423
2 changed files with 217 additions and 0 deletions
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202
lib/addns/dnsquery.c
View File

@ -371,6 +371,208 @@ fail:
return status;
}
/*********************************************************************
Async A record lookup.
*********************************************************************/
struct ads_dns_lookup_a_state {
uint8_t rcode;
size_t num_names;
char **hostnames;
struct samba_sockaddr *addrs;
};
static void ads_dns_lookup_a_done(struct tevent_req *subreq);
struct tevent_req *ads_dns_lookup_a_send(TALLOC_CTX *mem_ctx,
struct tevent_context *ev,
const char *name)
{
struct tevent_req *req = NULL, *subreq = NULL;
struct ads_dns_lookup_a_state *state = NULL;
req = tevent_req_create(mem_ctx, &state,
struct ads_dns_lookup_a_state);
if (req == NULL) {
return NULL;
}
subreq = dns_lookup_send(
state,
ev,
NULL,
name,
DNS_QCLASS_IN,
DNS_QTYPE_A);
if (tevent_req_nomem(subreq, req)) {
return tevent_req_post(req, ev);
}
tevent_req_set_callback(subreq, ads_dns_lookup_a_done, req);
return req;
}
static void ads_dns_lookup_a_done(struct tevent_req *subreq)
{
struct tevent_req *req = tevent_req_callback_data(
subreq, struct tevent_req);
struct ads_dns_lookup_a_state *state = tevent_req_data(
req, struct ads_dns_lookup_a_state);
int ret;
struct dns_name_packet *reply = NULL;
uint16_t i;
ret = dns_lookup_recv(subreq, state, &reply);
TALLOC_FREE(subreq);
if (ret != 0) {
tevent_req_nterror(req, map_nt_error_from_unix_common(ret));
return;
}
state->rcode = (reply->operation & DNS_RCODE);
if (state->rcode != DNS_RCODE_OK) {
/* Don't bother looking for answers. */
tevent_req_done(req);
return;
}
/*
* We don't care about CNAME answers here. We're
* just wanting an async name -> IPv4 lookup.
*/
for (i = 0; i < reply->ancount; i++) {
if (reply->answers[i].rr_type == DNS_QTYPE_A) {
state->num_names += 1;
}
}
state->hostnames = talloc_zero_array(state,
char *,
state->num_names);
if (tevent_req_nomem(state->hostnames, req)) {
return;
}
state->addrs = talloc_zero_array(state,
struct samba_sockaddr,
state->num_names);
if (tevent_req_nomem(state->addrs, req)) {
return;
}
state->num_names = 0;
for (i = 0; i < reply->ancount; i++) {
bool ok;
struct sockaddr_storage ss = {0};
struct dns_res_rec *an = &reply->answers[i];
if (an->rr_type != DNS_QTYPE_A) {
continue;
}
if (an->name == NULL) {
/* Can this happen? */
continue;
}
if (an->rdata.ipv4_record == NULL) {
/* Can this happen? */
continue;
}
ok = dns_res_rec_get_sockaddr(an,
&ss);
if (!ok) {
continue;
}
if (is_zero_addr(&ss)) {
continue;
}
state->addrs[state->num_names].u.ss = ss;
state->addrs[state->num_names].sa_socklen =
sizeof(struct sockaddr_in);
state->hostnames[state->num_names] = talloc_strdup(
state->hostnames,
an->name);
if (tevent_req_nomem(state->hostnames[state->num_names], req)) {
return;
}
state->num_names += 1;
}
tevent_req_done(req);
}
NTSTATUS ads_dns_lookup_a_recv(struct tevent_req *req,
TALLOC_CTX *mem_ctx,
uint8_t *rcode_out,
size_t *num_names_out,
char ***hostnames_out,
struct samba_sockaddr **addrs_out)
{
struct ads_dns_lookup_a_state *state = tevent_req_data(
req, struct ads_dns_lookup_a_state);
NTSTATUS status;
if (tevent_req_is_nterror(req, &status)) {
return status;
}
if (rcode_out != NULL) {
/*
* If we got no names, an upper layer may
* want to print a debug message.
*/
*rcode_out = state->rcode;
}
if (hostnames_out != NULL) {
*hostnames_out = talloc_move(mem_ctx,
&state->hostnames);
}
if (addrs_out != NULL) {
*addrs_out = talloc_move(mem_ctx,
&state->addrs);
}
*num_names_out = state->num_names;
tevent_req_received(req);
return NT_STATUS_OK;
}
/*********************************************************************
Simple wrapper for a DNS A query
*********************************************************************/
NTSTATUS ads_dns_lookup_a(TALLOC_CTX *ctx,
const char *name_in,
size_t *num_names_out,
char ***hostnames_out,
struct samba_sockaddr **addrs_out)
{
struct tevent_context *ev;
struct tevent_req *req;
NTSTATUS status = NT_STATUS_NO_MEMORY;
ev = samba_tevent_context_init(ctx);
if (ev == NULL) {
goto fail;
}
req = ads_dns_lookup_a_send(ev, ev, name_in);
if (req == NULL) {
goto fail;
}
if (!tevent_req_poll_ntstatus(req, ev, &status)) {
goto fail;
}
/*
* Sychronous doesn't need to care about the rcode or
* a copy of the name_in.
*/
status = ads_dns_lookup_a_recv(req,
ctx,
NULL,
num_names_out,
hostnames_out,
addrs_out);
fail:
TALLOC_FREE(ev);
return status;
}
/********************************************************************
Query with optional sitename.

15
lib/addns/dnsquery.h
View File

@ -48,6 +48,21 @@ NTSTATUS ads_dns_lookup_ns(TALLOC_CTX *ctx,
const char *dnsdomain,
struct dns_rr_ns **nslist,
int *numns);
struct tevent_req *ads_dns_lookup_a_send(TALLOC_CTX *mem_ctx,
struct tevent_context *ev,
const char *name);
NTSTATUS ads_dns_lookup_a_recv(struct tevent_req *req,
TALLOC_CTX *mem_ctx,
uint8_t *rcode_out,
size_t *num_names_out,
char ***hostnames_out,
struct samba_sockaddr **addrs_out);
NTSTATUS ads_dns_lookup_a(TALLOC_CTX *ctx,
const char *name_in,
size_t *num_names_out,
char ***hostnames_out,
struct samba_sockaddr **addrs_out);
NTSTATUS ads_dns_query_dcs(TALLOC_CTX *ctx,
const char *realm,
const char *sitename,