libdns: dns/tcp client

Same signature as the UDP client in the same file. This opens and closes
the socket per request. In the future, we might want to create a
persistent TCP connection for our internal DNS server's forwarder. That
will require proper handling of in-flight requests. Something for
another day.

Signed-off-by: Volker Lendecke <vl@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

diff --git a/libcli/dns/dns.c b/libcli/dns/dns.c
index 7d066d802c146414dcef0e827c9ce547b8ebbdfa..9e180fe3fc9855618c452acbb08cfcb91e5a89af 100644 (file)
--- a/libcli/dns/dns.c
+++ b/libcli/dns/dns.c
@@ -176,3 +176,222 @@ int dns_udp_request_recv(struct tevent_req *req,
 
        return 0;
 }
+
+struct dns_tcp_request_state {
+       struct tevent_context *ev;
+       struct tstream_context *stream;
+       const uint8_t *query;
+       size_t query_len;
+
+       uint8_t dns_msglen_hdr[2];
+       struct iovec iov[2];
+
+       size_t nread;
+       uint8_t *reply;
+};
+
+static void dns_tcp_request_connected(struct tevent_req *subreq);
+static void dns_tcp_request_sent(struct tevent_req *subreq);
+static int dns_tcp_request_next_vector(struct tstream_context *stream,
+                                      void *private_data,
+                                      TALLOC_CTX *mem_ctx,
+                                      struct iovec **_vector,
+                                      size_t *_count);
+static void dns_tcp_request_received(struct tevent_req *subreq);
+
+struct tevent_req *dns_tcp_request_send(TALLOC_CTX *mem_ctx,
+                                       struct tevent_context *ev,
+                                       const char *server_addr_string,
+                                       const uint8_t *query,
+                                       size_t query_len)
+{
+       struct tevent_req *req, *subreq;
+       struct dns_tcp_request_state *state;
+       struct tsocket_address *local, *remote;
+       int ret;
+
+       req = tevent_req_create(mem_ctx, &state,
+                               struct dns_tcp_request_state);
+       if (req == NULL) {
+               return NULL;
+       }
+       state->ev = ev;
+       state->query = query;
+       state->query_len = query_len;
+
+       if (query_len > UINT16_MAX) {
+               tevent_req_error(req, EMSGSIZE);
+               return tevent_req_post(req, ev);
+       }
+
+       ret = tsocket_address_inet_from_strings(state, "ip", NULL, 0, &local);
+       if (ret != 0) {
+               tevent_req_error(req, errno);
+               return tevent_req_post(req, ev);
+       }
+
+       ret = tsocket_address_inet_from_strings(
+               state, "ip", server_addr_string, DNS_SERVICE_PORT, &remote);
+       if (ret != 0) {
+               tevent_req_error(req, errno);
+               return tevent_req_post(req, ev);
+       }
+
+       subreq = tstream_inet_tcp_connect_send(state, state->ev,
+                                              local, remote);
+       if (tevent_req_nomem(subreq, req)) {
+               return tevent_req_post(req, ev);
+       }
+       tevent_req_set_callback(subreq, dns_tcp_request_connected, req);
+
+       return req;
+}
+
+static void dns_tcp_request_connected(struct tevent_req *subreq)
+{
+       struct tevent_req *req = tevent_req_callback_data(
+               subreq, struct tevent_req);
+       struct dns_tcp_request_state *state = tevent_req_data(
+               req, struct dns_tcp_request_state);
+       int ret, err;
+
+       ret = tstream_inet_tcp_connect_recv(subreq, &err, state,
+                                           &state->stream, NULL);
+       TALLOC_FREE(subreq);
+       if (ret == -1) {
+               tevent_req_error(req, err);
+               return;
+       }
+
+       RSSVAL(state->dns_msglen_hdr, 0, state->query_len);
+       state->iov[0] = (struct iovec) {
+               .iov_base = state->dns_msglen_hdr,
+               .iov_len = sizeof(state->dns_msglen_hdr)
+       };
+       state->iov[1] = (struct iovec) {
+               .iov_base = discard_const_p(void, state->query),
+               .iov_len = state->query_len
+       };
+
+       subreq = tstream_writev_send(state, state->ev, state->stream,
+                                    state->iov, ARRAY_SIZE(state->iov));
+       if (tevent_req_nomem(subreq, req)) {
+               return;
+       }
+       tevent_req_set_callback(subreq, dns_tcp_request_sent, req);
+}
+
+static void dns_tcp_request_sent(struct tevent_req *subreq)
+{
+       struct tevent_req *req = tevent_req_callback_data(
+               subreq, struct tevent_req);
+       struct dns_tcp_request_state *state = tevent_req_data(
+               req, struct dns_tcp_request_state);
+       int ret, err;
+
+       ret = tstream_writev_recv(subreq, &err);
+       TALLOC_FREE(subreq);
+       if (ret == -1) {
+               tevent_req_error(req, err);
+               return;
+       }
+
+       subreq = tstream_readv_pdu_send(state, state->ev, state->stream,
+                                       dns_tcp_request_next_vector, state);
+       if (tevent_req_nomem(subreq, req)) {
+               return;
+       }
+       tevent_req_set_callback(subreq, dns_tcp_request_received, req);
+}
+
+static int dns_tcp_request_next_vector(struct tstream_context *stream,
+                                      void *private_data,
+                                      TALLOC_CTX *mem_ctx,
+                                      struct iovec **_vector,
+                                      size_t *_count)
+{
+       struct dns_tcp_request_state *state = talloc_get_type_abort(
+               private_data, struct dns_tcp_request_state);
+       struct iovec *vector;
+       uint16_t msglen;
+
+       if (state->nread == 0) {
+               vector = talloc_array(mem_ctx, struct iovec, 1);
+               if (vector == NULL) {
+                       return -1;
+               }
+               vector[0] = (struct iovec) {
+                       .iov_base = state->dns_msglen_hdr,
+                       .iov_len = sizeof(state->dns_msglen_hdr)
+               };
+               state->nread = sizeof(state->dns_msglen_hdr);
+
+               *_vector = vector;
+               *_count = 1;
+               return 0;
+       }
+
+       if (state->nread == sizeof(state->dns_msglen_hdr)) {
+               msglen = RSVAL(state->dns_msglen_hdr, 0);
+
+               state->reply = talloc_array(state, uint8_t, msglen);
+               if (state->reply == NULL) {
+                       return -1;
+               }
+
+               vector = talloc_array(mem_ctx, struct iovec, 1);
+               if (vector == NULL) {
+                       return -1;
+               }
+               vector[0] = (struct iovec) {
+                       .iov_base = state->reply,
+                       .iov_len = msglen
+               };
+               state->nread += msglen;
+
+               *_vector = vector;
+               *_count = 1;
+               return 0;
+       }
+
+       *_vector = NULL;
+       *_count = 0;
+       return 0;
+}
+
+static void dns_tcp_request_received(struct tevent_req *subreq)
+{
+       struct tevent_req *req = tevent_req_callback_data(
+               subreq, struct tevent_req);
+       int ret, err;
+
+       ret = tstream_readv_pdu_recv(subreq, &err);
+       TALLOC_FREE(subreq);
+       if (ret == -1) {
+               tevent_req_error(req, err);
+               return;
+       }
+
+       tevent_req_done(req);
+}
+
+int dns_tcp_request_recv(struct tevent_req *req,
+                        TALLOC_CTX *mem_ctx,
+                        uint8_t **reply,
+                        size_t *reply_len)
+{
+       struct dns_tcp_request_state *state = tevent_req_data(
+               req, struct dns_tcp_request_state);
+       int err;
+
+       if (tevent_req_is_unix_error(req, &err)) {
+               tevent_req_received(req);
+               return err;
+       }
+
+       *reply_len = talloc_array_length(state->reply);
+       *reply = talloc_move(mem_ctx, &state->reply);
+       tevent_req_received(req);
+
+       return 0;
+}

diff --git a/libcli/dns/libdns.h b/libcli/dns/libdns.h
index 91353a8e84d5af00e44eb1af2a98579af5b30078..1fa73d3fb2279b9aa9475aec67047f7eaccab247 100644 (file)
--- a/libcli/dns/libdns.h
+++ b/libcli/dns/libdns.h
@@ -50,4 +50,14 @@ int dns_udp_request_recv(struct tevent_req *req,
                         uint8_t **reply,
                         size_t *reply_len);
 
+struct tevent_req *dns_tcp_request_send(TALLOC_CTX *mem_ctx,
+                                       struct tevent_context *ev,
+                                       const char *server_addr_string,
+                                       const uint8_t *query,
+                                       size_t query_len);
+int dns_tcp_request_recv(struct tevent_req *req,
+                        TALLOC_CTX *mem_ctx,
+                        uint8_t **reply,
+                        size_t *reply_len);
+
 #endif /*__LIBDNS_H__*/