Enable retries for SSL_ERROR_WANT_READ (#14120)

* enable retries for SSL_ERROR_WANT_READ

* only when bytes is <= 0

* treat ERROR_WANT_READ/WRITE as 0 bytes

* dont close connection on zero bytes

* reuse ssl connection

* treat zero bytes

* ifdef for old openssl

* revert check

2 files changed, 19 insertions, 13 deletions

diff --git a/web/server/web_client.c b/web/server/web_client.c
index 740f04e071..1606c09d39 100644
--- a/web/server/web_client.c
+++ b/web/server/web_client.c
@@ -1250,12 +1250,15 @@ static inline void web_client_send_http_header(struct web_client *w) {
         if(bytes > 0)
             w->stats_sent_bytes += bytes;
 
-        error("HTTP headers failed to be sent (I sent %zu bytes but the system sent %zd bytes). Closing web client."
-              , buffer_strlen(w->response.header_output)
-              , bytes);
+        if (bytes < 0) {
 
-        WEB_CLIENT_IS_DEAD(w);
-        return;
+            error("HTTP headers failed to be sent (I sent %zu bytes but the system sent %zd bytes). Closing web client."
+                  , buffer_strlen(w->response.header_output)
+                  , bytes);
+
+            WEB_CLIENT_IS_DEAD(w);
+            return;
+        }
     }
     else
         w->stats_sent_bytes += bytes;
@@ -1615,7 +1618,6 @@ ssize_t web_client_send_chunk_header(struct web_client *w, size_t len)
 
     else if(bytes == 0) {
         debug(D_WEB_CLIENT, "%llu: Did not send chunk header to the client.", w->id);
-        WEB_CLIENT_IS_DEAD(w);
     }
     else {
         debug(D_WEB_CLIENT, "%llu: Failed to send chunk header to client.", w->id);
@@ -1638,7 +1640,6 @@ ssize_t web_client_send_chunk_close(struct web_client *w)
 
     else if(bytes == 0) {
         debug(D_WEB_CLIENT, "%llu: Did not send chunk suffix to the client.", w->id);
-        WEB_CLIENT_IS_DEAD(w);
     }
     else {
         debug(D_WEB_CLIENT, "%llu: Failed to send chunk suffix to client.", w->id);
@@ -1661,7 +1662,6 @@ ssize_t web_client_send_chunk_finalize(struct web_client *w)
 
     else if(bytes == 0) {
         debug(D_WEB_CLIENT, "%llu: Did not send chunk finalize suffix to the client.", w->id);
-        WEB_CLIENT_IS_DEAD(w);
     }
     else {
         debug(D_WEB_CLIENT, "%llu: Failed to send chunk finalize suffix to client.", w->id);
@@ -1778,7 +1778,6 @@ ssize_t web_client_send_deflate(struct web_client *w)
         debug(D_WEB_CLIENT, "%llu: Did not send any bytes to the client (zhave = %zu, zsent = %zu, need to send = %zu).",
             w->id, w->response.zhave, w->response.zsent, w->response.zhave - w->response.zsent);
 
-        WEB_CLIENT_IS_DEAD(w);
     }
     else {
         debug(D_WEB_CLIENT, "%llu: Failed to send data to client.", w->id);
@@ -1831,7 +1830,6 @@ ssize_t web_client_send(struct web_client *w) {
     }
     else if(likely(bytes == 0)) {
         debug(D_WEB_CLIENT, "%llu: Did not send any bytes to the client.", w->id);
-        WEB_CLIENT_IS_DEAD(w);
     }
     else {
         debug(D_WEB_CLIENT, "%llu: Failed to send data to client.", w->id);
@@ -1931,10 +1929,11 @@ ssize_t web_client_receive(struct web_client *w)
         debug(D_WEB_CLIENT, "%llu: Received %zd bytes.", w->id, bytes);
         debug(D_WEB_DATA, "%llu: Received data: '%s'.", w->id, &w->response.data->buffer[old]);
     }
-    else {
+    else if (bytes < 0) {
         debug(D_WEB_CLIENT, "%llu: receive data failed.", w->id);
         WEB_CLIENT_IS_DEAD(w);
-    }
+    } else
+        debug(D_WEB_CLIENT, "%llu: Received %zd bytes.", w->id, bytes);
 
     return(bytes);
 }
diff --git a/web/server/web_client_cache.c b/web/server/web_client_cache.c
index 1fa5935803..51271a6006 100644
--- a/web/server/web_client_cache.c
+++ b/web/server/web_client_cache.c
@@ -11,7 +11,14 @@
 static void web_client_reuse_ssl(struct web_client *w) {
     if (netdata_ssl_srv_ctx) {
         if (w->ssl.conn) {
-            SSL_clear(w->ssl.conn);
+            SSL_SESSION *session = SSL_get_session(w->ssl.conn);
+            SSL *old = w->ssl.conn;
+            w->ssl.conn = SSL_new(netdata_ssl_srv_ctx);
+#if OPENSSL_VERSION_NUMBER >= OPENSSL_VERSION_111
+            if (SSL_SESSION_is_resumable(session))
+#endif
+                SSL_set_session(w->ssl.conn, session);
+            SSL_free(old);
         }
     }
 }