http: Merge branch 'http-max_connections-pr-592'

@jcoffland: "When the max connection limit is enabled and the limit is reached, the server will respond immediately with 503 Service Unavailable. This can be used to prevent servers from running out of file descriptors. This is better than request limiting because clients may make more than one request over a single connection. Blocking a request does not necessarily close the connection and free up a socket." * http-max_connections-pr-592: test: cover evhttp max connections Added evhttp max simultaneous connection limiting
azat · May 25, 2020 · 7426a56 · 7426a56
2 parents f10aaea + 95c1c20
commit 7426a56
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Showing 4 changed files with 130 additions and 1 deletion.
diff --git a/http-internal.h b/http-internal.h
@@ -147,6 +147,8 @@ struct evhttp {
 
  /* All live connections on this host. */
  struct evconq connections;
+ int connection_max;
+ int connection_cnt;
 
  TAILQ_HEAD(vhostsq, evhttp) virtualhosts;
 

diff --git a/http.c b/http.c
@@ -1336,6 +1336,7 @@ evhttp_connection_free(struct evhttp_connection *evcon)
  if (evcon->http_server != NULL) {
  struct evhttp *http = evcon->http_server;
  TAILQ_REMOVE(&http->connections, evcon, next);
+ http->connection_cnt--;
  }
 
  if (event_initialized(&evcon->retry_ev)) {
@@ -4115,6 +4116,21 @@ evhttp_set_max_body_size(struct evhttp* http, ev_ssize_t max_body_size)
  http->default_max_body_size = max_body_size;
 }
 
+void
+evhttp_set_max_connections(struct evhttp* http, int max_connections)
+{
+ if (max_connections < 0)
+ http->connection_max = 0;
+ else
+ http->connection_max = max_connections;
+}
+
+int
+evhttp_get_connection_count(struct evhttp* http)
+{
+ return http->connection_cnt;
+}
+
 void
 evhttp_set_default_content_type(struct evhttp *http,
  const char *content_type) {
@@ -4586,8 +4602,30 @@ evhttp_get_request(struct evhttp *http, evutil_socket_t fd,
  evcon->http_server = http;
  evcon->ext_method_cmp = http->ext_method_cmp;
  TAILQ_INSERT_TAIL(&http->connections, evcon, next);
+ http->connection_cnt++;
+
+ /* send "service unavailable" if we've reached the connection limit */
+ if (http->connection_max && http->connection_max < http->connection_cnt) {
+ struct evhttp_request *req;
+
+ if ((req = evhttp_request_new(evhttp_handle_request, http)) == NULL) {
+ evhttp_connection_free(evcon);
+ return;
+ }
+
+ req->evcon = evcon; /* the request owns the connection */
+ req->flags |= EVHTTP_REQ_OWN_CONNECTION;
+ req->kind = EVHTTP_REQUEST;
+ /* note, req->remote_host not needed since we don't read */
+
+ TAILQ_INSERT_TAIL(&evcon->requests, req, next);
+
+ /* send error to client */
+ evcon->state = EVCON_WRITING;
+ bufferevent_enable(evcon->bufev, EV_READ); /* enable close events */
+ evhttp_send_error(req, HTTP_SERVUNAVAIL, NULL);
 
- if (evhttp_associate_new_request_with_connection(evcon) == -1)
+ } else if (evhttp_associate_new_request_with_connection(evcon) == -1)
  evhttp_connection_free(evcon);
 }
 

diff --git a/include/event2/http.h b/include/event2/http.h
@@ -223,6 +223,24 @@ void evhttp_set_max_headers_size(struct evhttp* http, ev_ssize_t max_headers_siz
 EVENT2_EXPORT_SYMBOL
 void evhttp_set_max_body_size(struct evhttp* http, ev_ssize_t max_body_size);
 
+/**
+ * Set the maximum number of simultaneous connections for this server.
+ * A value of zero or less disables the limit.
+ *
+ * @param http the http server on which to set the max connection limit
+ * @param max_connections the maximum number of simultaneous connections or 0
+ */
+EVENT2_EXPORT_SYMBOL
+void evhttp_set_max_connections(struct evhttp* http, int max_connections);
+
+/**
+ * Get the current number of connections.
+ *
+ * @return The current number of connections for this server.
+ */
+EVENT2_EXPORT_SYMBOL
+int evhttp_get_connection_count(struct evhttp* http);
+
 /**
  Set the value to use for the Content-Type header when none was provided. If
  the content type string is NULL, the Content-Type header will not be

diff --git a/test/regress_http.c b/test/regress_http.c
@@ -5319,6 +5319,76 @@ http_timeout_read_server_test(void *arg)
 
 
 
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
+static void
+http_max_connections_test(void *arg)
+{
+ struct basic_test_data *data = arg;
+ ev_uint16_t port = 0;
+ struct evhttp *http = http_setup(&port, data->base, 0);
+ struct evhttp_connection *evcons[2];
+ struct http_newreqcb_test_state newreqcb_test_state;
+ unsigned n;
+
+ exit_base = data->base;
+ test_ok = 0;
+
+ memset(&newreqcb_test_state, 0, sizeof(newreqcb_test_state));
+ memset(evcons, 0, sizeof(evcons));
+
+ evhttp_set_max_connections(http, ARRAY_SIZE(evcons)-1);
+
+ for (n = 0; n < sizeof(evcons)/sizeof(evcons[0]); ++n) {
+ struct evhttp_connection* evcon = NULL;
+ struct evhttp_request *req = NULL;
+ evcons[n] = evhttp_connection_base_new(data->base, NULL, "127.0.0.1", port);
+ evcon = evcons[n];
+ evhttp_connection_set_retries(evcon, 0);
+
+ tt_assert(evcon);
+
+ req = evhttp_request_new(http_request_done_newreqcb, &newreqcb_test_state);
+ evhttp_add_header(evhttp_request_get_output_headers(req), "Connection", "close");
+ evhttp_request_set_error_cb(req, http_request_error_newreqcb);
+
+ /* We give ownership of the request to the connection */
+ if (evhttp_make_request(evcon, req, EVHTTP_REQ_GET, "/test") == -1) {
+ tt_abort_msg("Couldn't make request");
+ }
+
+ ++newreqcb_test_state.connections_started;
+ http_newreqcb_test_state_check(&newreqcb_test_state);
+ }
+
+ /* XXX: http_newreqcb_test_state_check will not stop the base, since:
+ * - connections_done == 2
+ * - connections_good == 1
+ *
+ * hence timeout
+ */
+ {
+ struct timeval tv = { 0, 300e3 };
+ event_base_loopexit(data->base, &tv);
+ }
+
+ event_base_dispatch(data->base);
+
+ http_newreqcb_test_state_check(&newreqcb_test_state);
+ tt_int_op(newreqcb_test_state.connections_error, ==, 0);
+ tt_int_op(newreqcb_test_state.connections_done, ==, 2);
+ tt_int_op(newreqcb_test_state.connections_good, ==, 1);
+
+end:
+ evhttp_free(http);
+
+ for (n = 0; n < ARRAY_SIZE(evcons); ++n) {
+ if (evcons[n]) {
+ evhttp_connection_free(evcons[n]);
+ }
+ }
+}
+
+
 #define HTTP_LEGACY(name) \
  { #name, run_legacy_test_fn, TT_ISOLATED|TT_LEGACY, &legacy_setup, \
  http_##name##_test }
@@ -5456,6 +5526,7 @@ struct testcase_t http_testcases[] = {
  HTTP(request_extra_body),
 
  HTTP(newreqcb),
+ HTTP(max_connections),
 
  HTTP(timeout_read_client),
  HTTP(timeout_read_server),