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https://gitlab.isc.org/isc-projects/bind9
synced 2025-08-31 06:25:31 +00:00
Refactor tcp_recv()
The tcp_recv() function used lot of gotos that made the function hard to read. Refactor the function by splitting it into smaller logical chunks.
This commit is contained in:
Ondřej Surý
Evan Hunt
@@ -595,6 +595,117 @@ done:
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dispentry_detach(&resp);
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}
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static isc_result_t
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tcp_recv_success(dns_dispatch_t *disp, isc_region_t *region, dns_qid_t *qid,
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isc_sockaddr_t *peer, dns_dispentry_t **respp) {
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isc_buffer_t source;
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dns_messageid_t id;
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unsigned int flags;
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unsigned int bucket;
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isc_result_t result = ISC_R_SUCCESS;
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dns_dispentry_t *resp = NULL;
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dispatch_log(disp, LVL(90), "success, length == %d, addr = %p",
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region->length, region->base);
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/*
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* Peek into the buffer to see what we can see.
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*/
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isc_buffer_init(&source, region->base, region->length);
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isc_buffer_add(&source, region->length);
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result = dns_message_peekheader(&source, &id, &flags);
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if (result != ISC_R_SUCCESS) {
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dispatch_log(disp, LVL(10), "got garbage packet");
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result = ISC_R_UNEXPECTED;
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goto next;
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}
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dispatch_log(disp, LVL(92),
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"got valid DNS message header, /QR %c, id %u",
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(((flags & DNS_MESSAGEFLAG_QR) != 0) ? '1' : '0'), id);
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/*
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* Look at the message flags. If it's a query, ignore it and keep
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* reading.
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*/
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if ((flags & DNS_MESSAGEFLAG_QR) == 0) {
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dispatch_log(disp, LVL(10), "got DNS query instead of answer");
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result = ISC_R_UNEXPECTED;
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goto next;
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}
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/*
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* We have a valid response; find the associated dispentry object
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* and call the caller back.
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*/
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bucket = dns_hash(qid, peer, id, disp->localport);
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LOCK(&qid->lock);
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resp = entry_search(qid, peer, id, disp->localport, bucket);
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if (resp != NULL) {
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dispentry_attach(resp, &(dns_dispentry_t *){ NULL });
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*respp = resp;
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} else {
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result = ISC_R_NOTFOUND;
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}
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dispatch_log(disp, LVL(90), "search for response in bucket %d: %s",
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bucket, isc_result_totext(result));
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UNLOCK(&qid->lock);
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next:
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dispatch_getnext(disp, NULL, -1);
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return (result);
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}
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static isc_result_t
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tcp_recv_timeout(dns_dispatch_t *disp, dns_dispentry_t **respp) {
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dns_dispentry_t *resp = ISC_LIST_HEAD(disp->active);
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if (resp != NULL) {
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dispentry_attach(resp, &(dns_dispentry_t *){ NULL });
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ISC_LIST_UNLINK(disp->active, resp, alink);
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ISC_LIST_APPEND(disp->active, resp, alink);
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*respp = resp;
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return (ISC_R_TIMEDOUT);
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}
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return (ISC_R_NOTFOUND);
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}
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static void
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tcp_recv_shutdown(dns_dispatch_t *disp, dns_displist_t *resps) {
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dns_dispentry_t *resp = NULL, *next = NULL;
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/*
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* If there are any active responses, shut them all down.
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*/
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for (resp = ISC_LIST_HEAD(disp->active); resp != NULL; resp = next) {
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next = ISC_LIST_NEXT(resp, alink);
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dispentry_attach(resp, &(dns_dispentry_t *){ NULL });
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ISC_LIST_UNLINK(disp->active, resp, alink);
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ISC_LIST_APPEND(*resps, resp, rlink);
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}
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}
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static void
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tcp_recv_done(dns_dispentry_t *resp, isc_result_t eresult,
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isc_region_t *region) {
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resp->response(eresult, region, resp->arg);
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dispentry_detach(&resp);
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}
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static void
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tcp_recv_cancelall(dns_displist_t *resps, isc_region_t *region) {
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dns_dispentry_t *resp = NULL, *next = NULL;
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for (resp = ISC_LIST_HEAD(*resps); resp != NULL; resp = next) {
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next = ISC_LIST_NEXT(resp, rlink);
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ISC_LIST_UNLINK(*resps, resp, rlink);
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resp->response(ISC_R_SHUTTINGDOWN, region, resp->arg);
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dispentry_detach(&resp);
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}
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}
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/*
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* General flow:
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*
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@@ -611,18 +722,12 @@ done:
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* restart.
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*/
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static void
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tcp_recv(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
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tcp_recv(isc_nmhandle_t *handle, isc_result_t result, isc_region_t *region,
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void *arg) {
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dns_dispatch_t *disp = (dns_dispatch_t *)arg;
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dns_dispentry_t *resp = NULL, *next = NULL;
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dns_messageid_t id;
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isc_result_t dres;
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unsigned int flags;
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unsigned int bucket;
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dns_dispentry_t *resp = NULL;
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dns_qid_t *qid = NULL;
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int level;
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char buf[ISC_SOCKADDR_FORMATSIZE];
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isc_buffer_t source;
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isc_sockaddr_t peer;
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dns_displist_t resps;
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@@ -630,29 +735,26 @@ tcp_recv(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
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qid = disp->mgr->qid;
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ISC_LIST_INIT(resps);
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LOCK(&disp->lock);
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dispatch_log(disp, LVL(90), "TCP read:%s:requests %d, buffers %d",
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isc_result_totext(eresult), disp->requests,
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isc_result_totext(result), disp->requests,
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disp->tcpbuffers);
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peer = isc_nmhandle_peeraddr(handle);
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ISC_LIST_INIT(resps);
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switch (eresult) {
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case ISC_R_SUCCESS:
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/* got our answer */
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break;
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switch (result) {
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case ISC_R_SHUTTINGDOWN:
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case ISC_R_CANCELED:
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case ISC_R_EOF:
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dispatch_log(disp, LVL(90), "shutting down: %s",
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isc_result_totext(eresult));
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/*
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* If there are any active responses, shut them all down.
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*/
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goto shutdown;
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case ISC_R_CONNECTIONRESET:
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isc_sockaddr_format(&peer, buf, sizeof(buf));
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dispatch_log(disp, LVL(90), "shutting down TCP: %s: %s", buf,
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isc_result_totext(result));
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tcp_recv_shutdown(disp, &resps);
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break;
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case ISC_R_TIMEDOUT:
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/*
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@@ -661,108 +763,53 @@ tcp_recv(isc_nmhandle_t *handle, isc_result_t eresult, isc_region_t *region,
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* active queue immediately, though, because the callback
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* might decide to keep waiting and leave it active.)
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*/
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resp = ISC_LIST_HEAD(disp->active);
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if (resp != NULL) {
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dispentry_attach(resp, &(dns_dispentry_t *){ NULL });
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ISC_LIST_UNLINK(disp->active, resp, alink);
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ISC_LIST_APPEND(disp->active, resp, alink);
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}
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goto done;
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result = tcp_recv_timeout(disp, &resp);
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break;
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case ISC_R_SUCCESS:
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/* We got an answer */
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result = tcp_recv_success(disp, region, qid, &peer, &resp);
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if (result == ISC_R_SUCCESS || result == ISC_R_NOTFOUND) {
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/*
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* It's a valid DNS response, which may or may not
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* have matched an outstanding query.
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*/
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break;
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}
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/* Got an invalid DNS response, terminate the connection */
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/* FALLTHROUGH */
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default:
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if (eresult == ISC_R_CONNECTIONRESET) {
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level = ISC_LOG_INFO;
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} else {
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level = ISC_LOG_ERROR;
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}
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isc_sockaddr_format(&peer, buf, sizeof(buf));
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dispatch_log(disp, level,
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dispatch_log(disp, ISC_LOG_ERROR,
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"shutting down due to TCP "
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"receive error: %s: %s",
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buf, isc_result_totext(eresult));
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/*
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* If there are any active responses, shut them all down.
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*/
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for (resp = ISC_LIST_HEAD(disp->active); resp != NULL;
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resp = next) {
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next = ISC_LIST_NEXT(resp, alink);
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dispentry_attach(resp, &(dns_dispentry_t *){ NULL });
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ISC_LIST_UNLINK(disp->active, resp, alink);
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ISC_LIST_APPEND(resps, resp, rlink);
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}
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goto done;
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buf, isc_result_totext(result));
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tcp_recv_shutdown(disp, &resps);
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break;
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}
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dispatch_log(disp, LVL(90), "success, length == %d, addr = %p",
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region->length, region->base);
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/*
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* Peek into the buffer to see what we can see.
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*/
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isc_buffer_init(&source, region->base, region->length);
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isc_buffer_add(&source, region->length);
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dres = dns_message_peekheader(&source, &id, &flags);
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if (dres != ISC_R_SUCCESS) {
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dispatch_log(disp, LVL(10), "got garbage packet");
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eresult = ISC_R_UNEXPECTED;
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goto shutdown;
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}
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dispatch_log(disp, LVL(92),
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"got valid DNS message header, /QR %c, id %u",
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(((flags & DNS_MESSAGEFLAG_QR) != 0) ? '1' : '0'), id);
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/*
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* Look at the message flags. If it's a query, stop reading.
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*/
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if ((flags & DNS_MESSAGEFLAG_QR) == 0) {
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dispatch_log(disp, LVL(10), "got DNS query instead of answer");
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eresult = ISC_R_UNEXPECTED;
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goto shutdown;
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}
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/*
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* We have a valid response; find the associated dispentry object
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* and call the caller back.
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*/
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bucket = dns_hash(qid, &peer, id, disp->localport);
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LOCK(&qid->lock);
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resp = entry_search(qid, &peer, id, disp->localport, bucket);
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if (resp != NULL) {
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dispentry_attach(resp, &(dns_dispentry_t *){ NULL });
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}
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dispatch_log(disp, LVL(90), "search for response in bucket %d: %s",
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bucket, (resp == NULL ? "not found" : "found"));
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UNLOCK(&qid->lock);
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dispatch_getnext(disp, NULL, -1);
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goto done;
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shutdown:
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for (resp = ISC_LIST_HEAD(disp->active); resp != NULL; resp = next) {
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next = ISC_LIST_NEXT(resp, alink);
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dispentry_attach(resp, &(dns_dispentry_t *){ NULL });
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ISC_LIST_UNLINK(disp->active, resp, alink);
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ISC_LIST_APPEND(resps, resp, rlink);
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}
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done:
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UNLOCK(&disp->lock);
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if (resp != NULL) {
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/* We got a matching response, or timed out */
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resp->response(eresult, region, resp->arg);
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dispentry_detach(&resp);
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} else {
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/* We're being shut down; cancel all outstanding resps */
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for (resp = ISC_LIST_HEAD(resps); resp != NULL; resp = next) {
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next = ISC_LIST_NEXT(resp, rlink);
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ISC_LIST_UNLINK(resps, resp, rlink);
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resp->response(ISC_R_SHUTTINGDOWN, region, resp->arg);
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dispentry_detach(&resp);
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}
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switch (result) {
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case ISC_R_SUCCESS:
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case ISC_R_TIMEDOUT:
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/*
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* Either we found a matching response, or we timed out
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* and canceled the oldest resp.
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*/
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INSIST(resp != NULL);
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tcp_recv_done(resp, result, region);
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break;
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case ISC_R_NOTFOUND:
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/*
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* Either we got a response that didn't match any active
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* resps, or we timed out but there *were* no active resps.
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*/
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break;
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default:
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/* We're being shut down; cancel all outstanding resps. */
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tcp_recv_cancelall(&resps, region);
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}
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dns_dispatch_detach(&disp);
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