<div dir="ltr"><pre style="color:rgb(0,0,0)">I'm currently running dnsmasq (with my patch applied) using the following script and everything seems to work fine actually - no errors reported.
(I have only added CAP_NET_BIND_SERVICE in order to be able to bind to port 67.)</pre><pre style="color:rgb(0,0,0)">#!/bin/bash
set -euo pipefail<br>SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"<br><br>PID_FILE=$SCRIPT_DIR/dnsmasq.pid<br><br>dnsmasq \<br>--pid-file=$PID_FILE \<br>--dhcp-leasefile=$SCRIPT_DIR/dnsmasq.leases \<br>--strict-order \<br>--bind-interfaces \<br>--dhcp-authoritative \<br>--no-ping \<br>--dhcp-broadcast \<br>--port=0 \<br>--conf-file= \<br>--no-hosts \<br>--interface=br-mgmt \<br>--listen-address=10.0.0.254 \<br>--dhcp-range=net:mgmt,10.0.0.1,10.0.0.250,255.255.255.0,10.0.0.255 \<br>--dhcp-option=mgmt,option:router \<br>--dhcp-host=52:54:00:00:00:01,id:*,net:mgmt,10.0.0.1 \<br>--dhcp-host=52:54:00:00:00:02,id:*,net:mgmt,10.0.0.2 \<br>--dhcp-host=52:54:00:00:00:03,id:*,net:mgmt,10.0.0.3 \<br>\<br>--interface=br-dth \<br>--listen-address=10.0.1.254 \<br>--dhcp-range=net:dth,10.0.1.1,10.0.1.250,255.255.255.0,10.0.1.255 \<br>--dhcp-option=dth,option:router \<br>--dhcp-option=dth,option:classless-static-route,<a href="http://10.235.0.0/16,10.0.1.254">10.235.0.0/16,10.0.1.254</a> \<br>--dhcp-host=52:54:00:00:01:01,id:*,net:dth,10.0.1.1 \<br>--dhcp-host=52:54:00:00:01:02,id:*,net:dth,10.0.1.2 \<br>--dhcp-host=52:54:00:00:01:03,id:*,net:dth,10.0.1.3 \<br>\<br>--interface=br-inet \<br>--listen-address=10.0.2.254 \<br>--dhcp-range=net:inet,10.0.2.1,10.0.2.250,255.255.255.0,10.0.2.255 \<br>--dhcp-option=inet,option:router,10.0.2.254 \<br>--dhcp-host=52:54:00:00:02:01,id:*,net:inet,10.0.2.1 \<br>--dhcp-host=52:54:00:00:02:02,id:*,net:inet,10.0.2.2 \<br>--dhcp-host=52:54:00:00:02:03,id:*,net:inet,10.0.2.3 \<br>\<br>--no-daemon<br></pre><pre style="color:rgb(0,0,0)"><br></pre><pre style="color:rgb(0,0,0)"><span style="font-family:Arial,Helvetica,sans-serif">this is the output:</span><br></pre><pre style="color:rgb(0,0,0)">dnsmasq: started, version 2.90deb2-1-g1ed783b DNS disabled
dnsmasq: compile time options: IPv6 GNU-getopt no-DBus no-UBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset no-nftset auth no-cryptohash no-DNSSEC loop-detect inotify dumpfile<br>dnsmasq-dhcp: DHCP, IP range 10.0.2.1 -- 10.0.2.250, lease time 1h
dnsmasq-dhcp: DHCP, IP range 10.0.1.1 -- 10.0.1.250, lease time 1h
dnsmasq-dhcp: DHCP, IP range 10.0.0.1 -- 10.0.0.250, lease time 1h
dnsmasq-dhcp: DHCPDISCOVER(br-mgmt) 52:54:00:00:00:01 <br>dnsmasq-dhcp: DHCPOFFER(br-mgmt) 10.0.0.1 52:54:00:00:00:01 <br>dnsmasq-dhcp: DHCPDISCOVER(br-dth) 52:54:00:00:01:01 <br>dnsmasq-dhcp: DHCPOFFER(br-dth) 10.0.1.1 52:54:00:00:01:01 <br>dnsmasq-dhcp: DHCPDISCOVER(br-inet) 52:54:00:00:02:01 <br>dnsmasq-dhcp: DHCPOFFER(br-inet) 10.0.2.1 52:54:00:00:02:01 <br>dnsmasq-dhcp: DHCPREQUEST(br-mgmt) 10.0.0.1 52:54:00:00:00:01 <br>dnsmasq-dhcp: DHCPACK(br-mgmt) 10.0.0.1 52:54:00:00:00:01 <br>dnsmasq-dhcp: DHCPREQUEST(br-inet) 10.0.2.1 52:54:00:00:02:01 <br>dnsmasq-dhcp: DHCPACK(br-inet) 10.0.2.1 52:54:00:00:02:01 <br>dnsmasq-dhcp: DHCPREQUEST(br-dth) 10.0.1.1 52:54:00:00:01:01 <br>dnsmasq-dhcp: DHCPACK(br-dth) 10.0.1.1 52:54:00:00:01:01<br></pre><pre style="color:rgb(0,0,0)"><br></pre><pre style="color:rgb(0,0,0)">inside the VM:</pre><pre style="color:rgb(0,0,0)">root@localhost:~# ip addr<br>1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000<br> link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00<br> inet <a href="http://127.0.0.1/8">127.0.0.1/8</a> scope host lo<br> valid_lft forever preferred_lft forever<br>2: enp0s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000<br> link/ether 52:54:00:00:00:01 brd ff:ff:ff:ff:ff:ff<br> inet <a href="http://10.0.0.1/24">10.0.0.1/24</a> metric 1024 brd 10.0.0.255 scope global dynamic enp0s1<br> valid_lft 3525sec preferred_lft 3525sec<br>3: enp0s2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000<br> link/ether 52:54:00:00:01:01 brd ff:ff:ff:ff:ff:ff<br> inet <a href="http://10.0.1.1/24">10.0.1.1/24</a> metric 1024 brd 10.0.1.255 scope global dynamic enp0s2<br> valid_lft 3525sec preferred_lft 3525sec<br>4: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000<br> link/ether 52:54:00:00:02:01 brd ff:ff:ff:ff:ff:ff<br> inet <a href="http://10.0.2.1/24">10.0.2.1/24</a> metric 1024 brd 10.0.2.255 scope global dynamic enp0s3<br> valid_lft 3525sec preferred_lft 3525sec<br></pre><pre style="color:rgb(0,0,0)"><br></pre><pre style="color:rgb(0,0,0)">Best regards,
Martin</pre></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 20, 2024 at 1:46 AM Simon Kelley <<a href="mailto:simon@thekelleys.org.uk">simon@thekelleys.org.uk</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">If you're doing DHCP, even if you're not sending ICMP ping packets, you <br>
still need CAP_NET_ADMIN, because the DHCP server has to be able to <br>
manipulate the ARP table.<br>
<br>
I guess you're starting dnsmasq without CAP_NET_ADMIN, dnsmasq is <br>
determining that it needs CPA_NET_ADMIN to run the DHCP server, and <br>
erroring out because it doesn't have it.<br>
<br>
<br>
Simon.<br>
<br>
<br>
On 19/02/2024 15:32, Martin Ivičič wrote:<br>
> Hello,<br>
> <br>
> I might have stumbled upon a minor bug in dnsmasq which causes NET_ADMIN <br>
> capability being required even if it's actually not needed (according to <br>
> provided command line arguments).<br>
> <br>
> diff --git a/src/dnsmasq.c b/src/dnsmasq.c<br>
> index 30fb419..cef42f6 100644<br>
> --- a/src/dnsmasq.c<br>
> +++ b/src/dnsmasq.c<br>
> @@ -313,9 +313,10 @@ int main (int argc, char **argv)<br>
> {<br>
> dhcp_init();<br>
> # ifdef HAVE_LINUX_NETWORK<br>
> - if (!option_bool(OPT_NO_PING))<br>
> - need_cap_net_raw = 1;<br>
> - need_cap_net_admin = 1;<br>
> + if (!option_bool(OPT_NO_PING)) {<br>
> + need_cap_net_raw = 1;<br>
> + need_cap_net_admin = 1;<br>
> + }<br>
> # endif<br>
> }<br>
> <br>
> Without this patch, with following arguments, dnsmasq ends with <br>
> "dnsmasq: process is missing required capability NET_ADMIN"<br>
> <br>
> src/dnsmasq \<br>
> --strict-order \<br>
> --bind-interfaces \<br>
> --interface=br-mgmt \<br>
> --listen-address=10.0.0.254 \<br>
> --dhcp-range=10.0.0.1,10.0.0.250 \<br>
> --dhcp-authoritative \<br>
> --no-ping \<br>
> --dhcp-broadcast \<br>
> --port=0 \<br>
> --conf-file= \<br>
> --pid-file=/tmp/dnsmasq.pid \<br>
> --dhcp-leasefile=/tmp/dnsmasq.leases \<br>
> --dhcp-no-override \<br>
> --no-daemon<br>
> <br>
> After applying the patch dnsmasq starts and runs fine.<br>
> <br>
> Best regards,<br>
> Martin<br>
> <br>
> <br>
> _______________________________________________<br>
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</blockquote></div>