From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id A31761FF140 for ; Thu, 15 Jan 2026 15:27:47 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 6DC3A4649; Thu, 15 Jan 2026 15:27:50 +0100 (CET) From: Stefan Hanreich To: pve-devel@lists.proxmox.com Date: Thu, 15 Jan 2026 15:27:44 +0100 Message-ID: <20260115142746.208819-1-s.hanreich@proxmox.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 X-SPAM-LEVEL: Spam detection results: 0 AWL -1.174 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment KAM_LAZY_DOMAIN_SECURITY 1 Sending domain does not have any anti-forgery methods KAM_MAILER 2 Automated Mailer Tag Left in Email RCVD_IN_VALIDITY_CERTIFIED_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. 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RDNS_NONE 0.793 Delivered to internal network by a host with no rDNS SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_NONE 0.001 SPF: sender does not publish an SPF Record Subject: [pve-devel] [PATCH pve-network v2 1/1] fix #5949: avoid dnsmasq segfault when subnet has no gateway X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Proxmox VE development discussion Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: pve-devel-bounces@lists.proxmox.com Sender: "pve-devel" When trying to start a guest with a network device in a VNet in a simple zone that has DHCP enabled - but no gateway configured - a SIGSEGV is triggered in dnsmasq. This seems to be an error in the dnsmasq dbus handler that tries to allocate a lease, which fails because there is no dhcp-range configured, and then leads to a segfault. Avoid the situation completely by always configuring a dhcp-range in IPv4 subnets, even if there is no gateway configured. Skip configuring the DHCP option that returns the router instead, which is the only place in the configure_subnet function that uses the gateway. Dnsmasq is configured to listen on an interface, so any DHCP messages that are received on this interface are dropped, because dnsmasq recognizes that there is no IP configured on this interface: Nov 26 16:35:49 ipam-test dnsmasq-dhcp[140272]: DHCP packet received on vnet1 which has no address Nov 26 16:35:57 ipam-test dnsmasq-dhcp[140272]: DHCP packet received on vnet1 which has no address The respective upstream fix is contained in commit eb601683 [1]. [1] https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=eb601683820723df89858cfa695aa131012f1a63 Signed-off-by: Stefan Hanreich --- Notes: Changes from v1: * added TODO comment * adjusted commit message * only run check for IPv4 subnets, since the error only occurs with IPv4 subnets src/PVE/Network/SDN/Dhcp/Dnsmasq.pm | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm index db22e12..fe46cbb 100644 --- a/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm +++ b/src/PVE/Network/SDN/Dhcp/Dnsmasq.pm @@ -138,14 +138,18 @@ sub add_ip_mapping { sub configure_subnet { my ($class, $config, $dhcpid, $vnetid, $subnet_config) = @_; - die "No gateway defined for subnet $subnet_config->{id}" - if !$subnet_config->{gateway}; - my $tag = $subnet_config->{id}; my ($zone, $network, $mask) = split(/-/, $tag); + my $is_ipv4 = Net::IP::ip_is_ipv4($network); + + # only die for IPv6 for now, since dnsmasq segfaults for IPv4 subnets + # without any gateway if no dhcp-range statement is configured (see #5949) + # TODO: enable check for IPv4 again as soon as fix is available. + die "No gateway configured for subnet $subnet_config->{id}" + if !$subnet_config->{gateway} && !$is_ipv4; - if (Net::IP::ip_is_ipv4($network)) { + if ($is_ipv4) { $mask = (2**$mask - 1) << (32 - $mask); $mask = join('.', unpack("C4", pack("N", $mask))); } @@ -155,7 +159,7 @@ sub configure_subnet { my $option_string; if (ip_is_ipv6($subnet_config->{network})) { $option_string = 'option6'; - } else { + } elsif ($subnet_config->{gateway}) { $option_string = 'option'; push @{$config}, "dhcp-option=tag:$tag,$option_string:router,$subnet_config->{gateway}"; } -- 2.47.3 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel