From 73a45af5c50d58867efc7f1778d7c2f9906f50d9 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Niklas=20Hamb=C3=BCchen?= Date: Sun, 12 Apr 2020 20:21:02 +0200 Subject: [PATCH] Warn if system capped requested socket buffer sizes. --- src/net_socket.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/src/net_socket.c b/src/net_socket.c index 206321cd..afe349d9 100644 --- a/src/net_socket.c +++ b/src/net_socket.c @@ -289,10 +289,44 @@ int setup_vpn_in_socket(const sockaddr_t *sa) { logger(DEBUG_ALWAYS, LOG_WARNING, "Can't set UDP SO_RCVBUF to %i: %s", udp_rcvbuf, sockstrerror(sockerrno)); } + { + // The system may cap the requested buffer size. + // Read back the value and check if it is now as requested. + int udp_rcvbuf_actual = -1; + socklen_t optlen = sizeof(udp_rcvbuf_actual); + + if(getsockopt(nfd, SOL_SOCKET, SO_RCVBUF, (void *)&udp_rcvbuf_actual, &optlen)) { + logger(DEBUG_ALWAYS, LOG_WARNING, "Can't read back UDP SO_RCVBUF: %s", sockstrerror(sockerrno)); + } else if(optlen != sizeof(udp_rcvbuf_actual)) { + logger(DEBUG_ALWAYS, LOG_WARNING, "Can't read back UDP SO_RCVBUF: Unexpected returned optlen %jd", (intmax_t) optlen); + } else { + if(udp_rcvbuf_actual != udp_rcvbuf) { + logger(DEBUG_ALWAYS, LOG_WARNING, "Can't set UDP SO_RCVBUF to %i, the system set it to %i instead", udp_rcvbuf, udp_rcvbuf_actual); + } + } + } + if(udp_sndbuf && setsockopt(nfd, SOL_SOCKET, SO_SNDBUF, (void *)&udp_sndbuf, sizeof(udp_sndbuf))) { logger(DEBUG_ALWAYS, LOG_WARNING, "Can't set UDP SO_SNDBUF to %i: %s", udp_sndbuf, sockstrerror(sockerrno)); } + { + // The system may cap the requested buffer size. + // Read back the value and check if it is now as requested. + int udp_sndbuf_actual = -1; + socklen_t optlen = sizeof(udp_sndbuf_actual); + + if(getsockopt(nfd, SOL_SOCKET, SO_SNDBUF, (void *)&udp_sndbuf_actual, &optlen)) { + logger(DEBUG_ALWAYS, LOG_WARNING, "Can't read back UDP SO_SNDBUF: %s", sockstrerror(sockerrno)); + } else if(optlen != sizeof(udp_sndbuf_actual)) { + logger(DEBUG_ALWAYS, LOG_WARNING, "Can't read back UDP SO_SNDBUF: Unexpected returned optlen %jd", (intmax_t) optlen); + } else { + if(udp_sndbuf_actual != udp_sndbuf) { + logger(DEBUG_ALWAYS, LOG_WARNING, "Can't set UDP SO_SNDBUF to %i, the system set it to %i instead", udp_sndbuf, udp_sndbuf_actual); + } + } + } + #if defined(IPV6_V6ONLY) if(sa->sa.sa_family == AF_INET6) { -- 2.20.1