[noPoll] Use of gethostbyname in noPoll library

Kale, Rahul Rahul.Kale en barco.com
Vie Oct 28 18:52:35 CEST 2016


I have narrowed down the cause of intermittent failures in our stress
test cases to the use of gethostbyname() in noPoll library.
This function is not thread safe under Linux (possibly other platforms too).

I fixed this by modifying  function nopoll_conn_sock_connect_opts()
This function is used for outbound client connections.
Our application makes multiple websocket connections to
different hosts in one process. The problem was revealed when
I started using dns hosts names instead of IP addresses.
I updated the function to use getaddrinfo() instead of gethostbyname().
My modifications fixed the stress test failures.
There is another place gethostbyname is used that I did not
fix since we are not yet using the server (listen) mode.

Below is my modified function for reference:

NOPOLL_SOCKET nopoll_conn_sock_connect_opts (noPollCtx       * ctx,
                                                                                     const char      * host,
                                                                                     const char      * port,
                                                                                     noPollConnOpts  * options)
                NOPOLL_SOCKET        session;
                struct addrinfo hints, *servinfo, *p;
                int rc;

                memset(&hints, 0, sizeof hints);
                hints.ai_family = AF_INET; /* force IPv4 */
                hints.ai_socktype = SOCK_STREAM;
                if ((rc = getaddrinfo(host, port, &hints, &servinfo)) != 0) {
                                nopoll_log (ctx, NOPOLL_LEVEL_DEBUG, "unable to resolve host name %s", host);
                                return -1;
                p = servinfo;
                if (p == NULL) {
                                nopoll_log (ctx, NOPOLL_LEVEL_DEBUG, "unable to retrieve address for host name %s", host);
                                return -1;

                /* create the socket and check if it */
                session      = socket (AF_INET, SOCK_STREAM, 0);
                if (session == NOPOLL_INVALID_SOCKET) {
                                nopoll_log (ctx, NOPOLL_LEVEL_CRITICAL, "unable to create socket");
                                return -1;
                } /* end if */

                /* disable nagle */
                nopoll_conn_set_sock_tcp_nodelay (session, nopoll_true);

                /* bind to specified interface */
                if( nopoll_true != nopoll_conn_set_bind_interface (session, options) ) {
                                nopoll_log (ctx, NOPOLL_LEVEL_CRITICAL, "unable to bind to specified interface");
                                nopoll_close_socket (session);
                                return -1;
                } /* end if */

                /* set non blocking status */
                nopoll_conn_set_sock_block (session, nopoll_false);

                /* do a tcp connect */
                if (connect (session, p->ai_addr, p->ai_addrlen) < 0) {
                                if(errno != NOPOLL_EINPROGRESS && errno != NOPOLL_EWOULDBLOCK && errno != NOPOLL_ENOTCONN) {
                                        shutdown (session, SHUT_RDWR);
                        nopoll_close_socket (session);

                                                nopoll_log (ctx, NOPOLL_LEVEL_WARNING, "unable to connect to remote host %s:%s errno=%d",
                                                                    host, port, errno);
                                                return -1;
                                } /* end if */
                } /* end if */


                /* return socket created */
                return session;



Rahul Kale

IP Video Systems
Barco, Inc
1287 Anvilwood Ave
Sunnyvale, CA  94089

Tel  +1 408 400 4238

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