<div dir="ltr">Our intent is to run tests in CI where we can't use root user or set any capabilities (eventually we'll be running with --dhcp-alternate-port=1067,1068 as well)<div>What do you think about the following?<br></div><div><br></div><div>diff --git a/src/dnsmasq.c b/src/dnsmasq.c<br>index 30fb419..5969e01 100644<br>--- a/src/dnsmasq.c<br>+++ b/src/dnsmasq.c<br>@@ -315,7 +315,8 @@ int main (int argc, char **argv)<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) || daemon->force_broadcast == NULL || daemon->force_broadcast->list != NULL)<br>+ need_cap_net_admin = 1;<br> # endif<br> }<br><div><br></div></div><div>Best regards,</div><div>Martin</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Feb 20, 2024 at 10:21 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">Ah, this is working because you include --dhcp-broadcast, which avoids <br>
the ARP-cache access.<br>
<br>
I'm not clear why you want to avoid CAP_NET_ADMIN, but a correct patch <br>
to do that would only not set need_cap_netadmin when --broadcast is set, <br>
and only when it's set unconditionally, without tags.<br>
<br>
Cheers,<br>
<br>
Simon.<br>
<br>
<br>
On 20/02/2024 00:50, Martin Ivičič wrote:<br>
> I'm currently running dnsmasq (with my patch applied) using the following script and everything seems to work fine actually - no errors reported.<br>
> (I have only added CAP_NET_BIND_SERVICE in order to be able to bind to port 67.)<br>
> <br>
> #!/bin/bash<br>
> 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" rel="noreferrer" target="_blank">10.235.0.0/16,10.0.1.254</a> <<a href="http://10.235.0.0/16,10.0.1.254" rel="noreferrer" target="_blank">http://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>
> <br>
> <br>
> this is the output:<br>
> <br>
> dnsmasq: started, version 2.90deb2-1-g1ed783b DNS disabled<br>
> 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<br>
> dnsmasq-dhcp: DHCP, IP range 10.0.1.1 -- 10.0.1.250, lease time 1h<br>
> dnsmasq-dhcp: DHCP, IP range 10.0.0.1 -- 10.0.0.250, lease time 1h<br>
> 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>
> <br>
> <br>
> inside the VM:<br>
> <br>
> 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>
> inet127.0.0.1/8 <<a href="http://127.0.0.1/8" rel="noreferrer" target="_blank">http://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>
> inet10.0.0.1/24 <<a href="http://10.0.0.1/24" rel="noreferrer" target="_blank">http://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>
> inet10.0.1.1/24 <<a href="http://10.0.1.1/24" rel="noreferrer" target="_blank">http://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>
> inet10.0.2.1/24 <<a href="http://10.0.2.1/24" rel="noreferrer" target="_blank">http://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>
> <br>
> <br>
> Best regards,<br>
> Martin<br>
> <br>
> <br>
> On Tue, Feb 20, 2024 at 1:46 AM Simon Kelley <<a href="mailto:simon@thekelleys.org.uk" target="_blank">simon@thekelleys.org.uk</a> <br>
> <mailto:<a href="mailto:simon@thekelleys.org.uk" target="_blank">simon@thekelleys.org.uk</a>>> wrote:<br>
> <br>
> 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<br>
> NET_ADMIN<br>
> > capability being required even if it's actually not needed<br>
> (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>
> > Dnsmasq-discuss mailing list<br>
> > <a href="mailto:Dnsmasq-discuss@lists.thekelleys.org.uk" target="_blank">Dnsmasq-discuss@lists.thekelleys.org.uk</a><br>
> <mailto:<a href="mailto:Dnsmasq-discuss@lists.thekelleys.org.uk" target="_blank">Dnsmasq-discuss@lists.thekelleys.org.uk</a>><br>
> ><br>
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> <br>
> <br>
> _______________________________________________<br>
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> <br>
</blockquote></div>