From 89382c3de5bc2250b1dad1c42c1f73d5ec6febda Mon Sep 17 00:00:00 2001 From: Knut Omang Date: Mon, 7 Aug 2017 12:58:40 +0200 Subject: sockets: factor out a new try_bind() function A refactoring step to prepare for the problem exposed by the test-listen test in the previous commit. Simplify and reorganize the IPv6 specific extra measures and move it out of the for loop to increase code readability. No semantic changes. Signed-off-by: Knut Omang Reviewed-by: Daniel P. Berrange Signed-off-by: Daniel P. Berrange --- util/qemu-sockets.c | 69 ++++++++++++++++++++++++++++++----------------------- 1 file changed, 39 insertions(+), 30 deletions(-) (limited to 'util') diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index d149383..211ebad 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -149,6 +149,44 @@ int inet_ai_family_from_address(InetSocketAddress *addr, return PF_UNSPEC; } +static int try_bind(int socket, InetSocketAddress *saddr, struct addrinfo *e) +{ +#ifndef IPV6_V6ONLY + return bind(socket, e->ai_addr, e->ai_addrlen); +#else + /* + * Deals with first & last cases in matrix in comment + * for inet_ai_family_from_address(). + */ + int v6only = + ((!saddr->has_ipv4 && !saddr->has_ipv6) || + (saddr->has_ipv4 && saddr->ipv4 && + saddr->has_ipv6 && saddr->ipv6)) ? 0 : 1; + int stat; + + rebind: + if (e->ai_family == PF_INET6) { + qemu_setsockopt(socket, IPPROTO_IPV6, IPV6_V6ONLY, &v6only, + sizeof(v6only)); + } + + stat = bind(socket, e->ai_addr, e->ai_addrlen); + if (!stat) { + return 0; + } + + /* If we got EADDRINUSE from an IPv6 bind & v6only is unset, + * it could be that the IPv4 port is already claimed, so retry + * with v6only set + */ + if (e->ai_family == PF_INET6 && errno == EADDRINUSE && !v6only) { + v6only = 1; + goto rebind; + } + return stat; +#endif +} + static int inet_listen_saddr(InetSocketAddress *saddr, int port_offset, bool update_addr, @@ -228,39 +266,10 @@ static int inet_listen_saddr(InetSocketAddress *saddr, port_min = inet_getport(e); port_max = saddr->has_to ? saddr->to + port_offset : port_min; for (p = port_min; p <= port_max; p++) { -#ifdef IPV6_V6ONLY - /* - * Deals with first & last cases in matrix in comment - * for inet_ai_family_from_address(). - */ - int v6only = - ((!saddr->has_ipv4 && !saddr->has_ipv6) || - (saddr->has_ipv4 && saddr->ipv4 && - saddr->has_ipv6 && saddr->ipv6)) ? 0 : 1; -#endif inet_setport(e, p); -#ifdef IPV6_V6ONLY - rebind: - if (e->ai_family == PF_INET6) { - qemu_setsockopt(slisten, IPPROTO_IPV6, IPV6_V6ONLY, &v6only, - sizeof(v6only)); - } -#endif - if (bind(slisten, e->ai_addr, e->ai_addrlen) == 0) { + if (try_bind(slisten, saddr, e) >= 0) { goto listen; } - -#ifdef IPV6_V6ONLY - /* If we got EADDRINUSE from an IPv6 bind & V6ONLY is unset, - * it could be that the IPv4 port is already claimed, so retry - * with V6ONLY set - */ - if (e->ai_family == PF_INET6 && errno == EADDRINUSE && !v6only) { - v6only = 1; - goto rebind; - } -#endif - if (p == port_max) { if (!e->ai_next) { error_setg_errno(errp, errno, "Failed to bind socket"); -- cgit v1.1 From 39f80521df1e7f1252960d1ada2bd1a41d4d2cd3 Mon Sep 17 00:00:00 2001 From: Knut Omang Date: Mon, 7 Aug 2017 12:58:41 +0200 Subject: sockets: factor out create_fast_reuse_socket Another refactoring step to prepare for fixing the problem exposed with the test-listen test in the previous commit Signed-off-by: Knut Omang Reviewed-by: Daniel P. Berrange Signed-off-by: Daniel P. Berrange --- util/qemu-sockets.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) (limited to 'util') diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index 211ebad..65f6dcd 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -149,6 +149,16 @@ int inet_ai_family_from_address(InetSocketAddress *addr, return PF_UNSPEC; } +static int create_fast_reuse_socket(struct addrinfo *e) +{ + int slisten = qemu_socket(e->ai_family, e->ai_socktype, e->ai_protocol); + if (slisten < 0) { + return -1; + } + socket_set_fast_reuse(slisten); + return slisten; +} + static int try_bind(int socket, InetSocketAddress *saddr, struct addrinfo *e) { #ifndef IPV6_V6ONLY @@ -253,7 +263,8 @@ static int inet_listen_saddr(InetSocketAddress *saddr, getnameinfo((struct sockaddr*)e->ai_addr,e->ai_addrlen, uaddr,INET6_ADDRSTRLEN,uport,32, NI_NUMERICHOST | NI_NUMERICSERV); - slisten = qemu_socket(e->ai_family, e->ai_socktype, e->ai_protocol); + + slisten = create_fast_reuse_socket(e); if (slisten < 0) { if (!e->ai_next) { error_setg_errno(errp, errno, "Failed to create socket"); @@ -261,8 +272,6 @@ static int inet_listen_saddr(InetSocketAddress *saddr, continue; } - socket_set_fast_reuse(slisten); - port_min = inet_getport(e); port_max = saddr->has_to ? saddr->to + port_offset : port_min; for (p = port_min; p <= port_max; p++) { -- cgit v1.1 From 9cf961bba74d433db76a110917ac70aecc2ebcc4 Mon Sep 17 00:00:00 2001 From: Knut Omang Date: Mon, 7 Aug 2017 12:58:42 +0200 Subject: sockets: Handle race condition between binds to the same port If an offset of ports is specified to the inet_listen_saddr function(), and two or more processes tries to bind from these ports at the same time, occasionally more than one process may be able to bind to the same port. The condition is detected by listen() but too late to avoid a failure. This function is called by socket_listen() and used by all socket listening code in QEMU, so all cases where any form of dynamic port selection is used should be subject to this issue. Add code to close and re-establish the socket when this condition is observed, hiding the race condition from the user. Also clean up some issues with error handling to allow more accurate reporting of the cause of an error. This has been developed and tested by means of the test-listen unit test in the previous commit. Enable the test for make check now that it passes. Reviewed-by: Bhavesh Davda Reviewed-by: Yuval Shaia Reviewed-by: Girish Moodalbail Signed-off-by: Knut Omang Reviewed-by: Daniel P. Berrange Signed-off-by: Daniel P. Berrange --- util/qemu-sockets.c | 58 +++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 41 insertions(+), 17 deletions(-) (limited to 'util') diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c index 65f6dcd..b47fb45 100644 --- a/util/qemu-sockets.c +++ b/util/qemu-sockets.c @@ -206,7 +206,10 @@ static int inet_listen_saddr(InetSocketAddress *saddr, char port[33]; char uaddr[INET6_ADDRSTRLEN+1]; char uport[33]; - int slisten, rc, port_min, port_max, p; + int rc, port_min, port_max, p; + int slisten = 0; + int saved_errno = 0; + bool socket_created = false; Error *err = NULL; memset(&ai,0, sizeof(ai)); @@ -258,7 +261,7 @@ static int inet_listen_saddr(InetSocketAddress *saddr, return -1; } - /* create socket + bind */ + /* create socket + bind/listen */ for (e = res; e != NULL; e = e->ai_next) { getnameinfo((struct sockaddr*)e->ai_addr,e->ai_addrlen, uaddr,INET6_ADDRSTRLEN,uport,32, @@ -266,37 +269,58 @@ static int inet_listen_saddr(InetSocketAddress *saddr, slisten = create_fast_reuse_socket(e); if (slisten < 0) { - if (!e->ai_next) { - error_setg_errno(errp, errno, "Failed to create socket"); - } continue; } + socket_created = true; port_min = inet_getport(e); port_max = saddr->has_to ? saddr->to + port_offset : port_min; for (p = port_min; p <= port_max; p++) { inet_setport(e, p); - if (try_bind(slisten, saddr, e) >= 0) { - goto listen; - } - if (p == port_max) { - if (!e->ai_next) { + rc = try_bind(slisten, saddr, e); + if (rc) { + if (errno == EADDRINUSE) { + continue; + } else { error_setg_errno(errp, errno, "Failed to bind socket"); + goto listen_failed; } } + if (!listen(slisten, 1)) { + goto listen_ok; + } + if (errno != EADDRINUSE) { + error_setg_errno(errp, errno, "Failed to listen on socket"); + goto listen_failed; + } + /* Someone else managed to bind to the same port and beat us + * to listen on it! Socket semantics does not allow us to + * recover from this situation, so we need to recreate the + * socket to allow bind attempts for subsequent ports: + */ + closesocket(slisten); + slisten = create_fast_reuse_socket(e); + if (slisten < 0) { + error_setg_errno(errp, errno, + "Failed to recreate failed listening socket"); + goto listen_failed; + } } + } + error_setg_errno(errp, errno, + socket_created ? + "Failed to find an available port" : + "Failed to create a socket"); +listen_failed: + saved_errno = errno; + if (slisten >= 0) { closesocket(slisten); } freeaddrinfo(res); + errno = saved_errno; return -1; -listen: - if (listen(slisten,1) != 0) { - error_setg_errno(errp, errno, "Failed to listen on socket"); - closesocket(slisten); - freeaddrinfo(res); - return -1; - } +listen_ok: if (update_addr) { g_free(saddr->host); saddr->host = g_strdup(uaddr); -- cgit v1.1