From 0df0edc49ce4acb96c8e16bdf0fcee1eedfd91f0 Mon Sep 17 00:00:00 2001 From: Sebastian Marsching Date: Mon, 15 Sep 2025 13:05:07 +0200 Subject: [PATCH] Bugfix: Set broadcast address on interface. This fixes a problem that was introduced in OpenVPN 2.5. Previously, the ifconfig utility was used for adding the local address to an interface. This utility automatically sets the correct broadcast address based on the given unicast address and netmask. Due to switching to iproute and Netlink, this does not happen automatically any longer, which means that applications that rely on broadcasts do not work correctly. This patch fixes this issue both when using iproute (by telling iproute to set the broadcast address based on the local address and prefix) and when using Netlink (by calculating the correct broadcast address and setting it). Signed-off-by: Sebastian Marsching Acked-by: Antonio Quartulli Message-Id: <20250915110507.20557-1-sebastian-git-2016@marsching.com> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg33131.html Signed-off-by: Gert Doering --- src/openvpn/networking_iproute2.c | 2 +- src/openvpn/networking_sitnl.c | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/src/openvpn/networking_iproute2.c b/src/openvpn/networking_iproute2.c index e9be3a455..773571d6d 100644 --- a/src/openvpn/networking_iproute2.c +++ b/src/openvpn/networking_iproute2.c @@ -150,7 +150,7 @@ net_addr_v4_add(openvpn_net_ctx_t *ctx, const char *iface, const in_addr_t *addr const char *addr_str = print_in_addr_t(*addr, 0, &ctx->gc); - argv_printf(&argv, "%s addr add dev %s %s/%d", iproute_path, iface, addr_str, prefixlen); + argv_printf(&argv, "%s addr add dev %s %s/%d broadcast +", iproute_path, iface, addr_str, prefixlen); argv_msg(M_INFO, &argv); openvpn_execve_check(&argv, ctx->es, S_FATAL, "Linux ip addr add failed"); diff --git a/src/openvpn/networking_sitnl.c b/src/openvpn/networking_sitnl.c index 4210e92c5..00d61067f 100644 --- a/src/openvpn/networking_sitnl.c +++ b/src/openvpn/networking_sitnl.c @@ -31,6 +31,7 @@ #include "misc.h" #include "networking.h" #include "proto.h" +#include "route.h" #include #include @@ -803,6 +804,13 @@ sitnl_addr_set(int cmd, uint32_t flags, int ifindex, sa_family_t af_family, SITNL_ADDATTR(&req.n, sizeof(req), IFA_LOCAL, local, size); } + if (af_family == AF_INET && local && !remote && prefixlen <= 30) + { + inet_address_t broadcast = *local; + broadcast.ipv4 |= htonl(~netbits_to_netmask(prefixlen)); + SITNL_ADDATTR(&req.n, sizeof(req), IFA_BROADCAST, &broadcast, size); + } + ret = sitnl_send(&req.n, 0, 0, NULL, NULL); if (ret == -EEXIST) { -- 2.47.3