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)
What do you think about the following?
diff --git a/src/dnsmasq.c b/src/dnsmasq.c
index 30fb419..5969e01 100644
--- a/src/dnsmasq.c
+++ b/src/dnsmasq.c
@@ -315,7 +315,8 @@ int main (int argc, char **argv)
# ifdef HAVE_LINUX_NETWORK
if (!option_bool(OPT_NO_PING))
need_cap_net_raw = 1;
- need_cap_net_admin = 1;
+ if (!option_bool(OPT_NO_PING) || daemon->force_broadcast == NULL ||
daemon->force_broadcast->list != NULL)
+ need_cap_net_admin = 1;
# endif
}
Best regards,
Martin
On Tue, Feb 20, 2024 at 10:21 AM Simon Kelley <si...@thekelleys.org.uk>
wrote:
> Ah, this is working because you include --dhcp-broadcast, which avoids
> the ARP-cache access.
>
> I'm not clear why you want to avoid CAP_NET_ADMIN, but a correct patch
> to do that would only not set need_cap_netadmin when --broadcast is set,
> and only when it's set unconditionally, without tags.
>
> Cheers,
>
> Simon.
>
>
> On 20/02/2024 00:50, Martin Ivičič wrote:
> > 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.)
> >
> > #!/bin/bash
> > set -euo pipefail
> > SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd
> )"
> >
> > PID_FILE=$SCRIPT_DIR/dnsmasq.pid
> >
> > dnsmasq \
> > --pid-file=$PID_FILE \
> > --dhcp-leasefile=$SCRIPT_DIR/dnsmasq.leases \
> > --strict-order \
> > --bind-interfaces \
> > --dhcp-authoritative \
> > --no-ping \
> > --dhcp-broadcast \
> > --port=0 \
> > --conf-file= \
> > --no-hosts \
> > --interface=br-mgmt \
> > --listen-address=10.0.0.254 \
> > --dhcp-range=net:mgmt,10.0.0.1,10.0.0.250,255.255.255.0,10.0.0.255 \
> > --dhcp-option=mgmt,option:router \
> > --dhcp-host=52:54:00:00:00:01,id:*,net:mgmt,10.0.0.1 \
> > --dhcp-host=52:54:00:00:00:02,id:*,net:mgmt,10.0.0.2 \
> > --dhcp-host=52:54:00:00:00:03,id:*,net:mgmt,10.0.0.3 \
> > \
> > --interface=br-dth \
> > --listen-address=10.0.1.254 \
> > --dhcp-range=net:dth,10.0.1.1,10.0.1.250,255.255.255.0,10.0.1.255 \
> > --dhcp-option=dth,option:router \
> > --dhcp-option=dth,option:classless-static-route,10.235.0.0/16,10.0.1.254
> <http://10.235.0.0/16,10.0.1.254> \
> > --dhcp-host=52:54:00:00:01:01,id:*,net:dth,10.0.1.1 \
> > --dhcp-host=52:54:00:00:01:02,id:*,net:dth,10.0.1.2 \
> > --dhcp-host=52:54:00:00:01:03,id:*,net:dth,10.0.1.3 \
> > \
> > --interface=br-inet \
> > --listen-address=10.0.2.254 \
> > --dhcp-range=net:inet,10.0.2.1,10.0.2.250,255.255.255.0,10.0.2.255 \
> > --dhcp-option=inet,option:router,10.0.2.254 \
> > --dhcp-host=52:54:00:00:02:01,id:*,net:inet,10.0.2.1 \
> > --dhcp-host=52:54:00:00:02:02,id:*,net:inet,10.0.2.2 \
> > --dhcp-host=52:54:00:00:02:03,id:*,net:inet,10.0.2.3 \
> > \
> > --no-daemon
> >
> >
> > this is the output:
> >
> > 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
> > 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
> > dnsmasq-dhcp: DHCPOFFER(br-mgmt) 10.0.0.1 52:54:00:00:00:01
> > dnsmasq-dhcp: DHCPDISCOVER(br-dth) 52:54:00:00:01:01
> > dnsmasq-dhcp: DHCPOFFER(br-dth) 10.0.1.1 52:54:00:00:01:01
> > dnsmasq-dhcp: DHCPDISCOVER(br-inet) 52:54:00:00:02:01
> > dnsmasq-dhcp: DHCPOFFER(br-inet) 10.0.2.1 52:54:00:00:02:01
> > dnsmasq-dhcp: DHCPREQUEST(br-mgmt) 10.0.0.1 52:54:00:00:00:01
> > dnsmasq-dhcp: DHCPACK(br-mgmt) 10.0.0.1 52:54:00:00:00:01
> > dnsmasq-dhcp: DHCPREQUEST(br-inet) 10.0.2.1 52:54:00:00:02:01
> > dnsmasq-dhcp: DHCPACK(br-inet) 10.0.2.1 52:54:00:00:02:01
> > dnsmasq-dhcp: DHCPREQUEST(br-dth) 10.0.1.1 52:54:00:00:01:01
> > dnsmasq-dhcp: DHCPACK(br-dth) 10.0.1.1 52:54:00:00:01:01
> >
> >
> > inside the VM:
> >
> > root@localhost:~# ip addr
> > 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
> group default qlen 1000
> > link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
> > inet127.0.0.1/8 <http://127.0.0.1/8> scope host lo
> > valid_lft forever preferred_lft forever
> > 2: enp0s1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
> state UP group default qlen 1000
> > link/ether 52:54:00:00:00:01 brd ff:ff:ff:ff:ff:ff
> > inet10.0.0.1/24 <http://10.0.0.1/24> metric 1024 brd 10.0.0.255
> scope global dynamic enp0s1
> > valid_lft 3525sec preferred_lft 3525sec
> > 3: enp0s2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
> state UP group default qlen 1000
> > link/ether 52:54:00:00:01:01 brd ff:ff:ff:ff:ff:ff
> > inet10.0.1.1/24 <http://10.0.1.1/24> metric 1024 brd 10.0.1.255
> scope global dynamic enp0s2
> > valid_lft 3525sec preferred_lft 3525sec
> > 4: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast
> state UP group default qlen 1000
> > link/ether 52:54:00:00:02:01 brd ff:ff:ff:ff:ff:ff
> > inet10.0.2.1/24 <http://10.0.2.1/24> metric 1024 brd 10.0.2.255
> scope global dynamic enp0s3
> > valid_lft 3525sec preferred_lft 3525sec
> >
> >
> > Best regards,
> > Martin
> >
> >
> > On Tue, Feb 20, 2024 at 1:46 AM Simon Kelley <si...@thekelleys.org.uk
> > <mailto:si...@thekelleys.org.uk>> wrote:
> >
> > If you're doing DHCP, even if you're not sending ICMP ping packets,
> you
> > still need CAP_NET_ADMIN, because the DHCP server has to be able to
> > manipulate the ARP table.
> >
> > I guess you're starting dnsmasq without CAP_NET_ADMIN, dnsmasq is
> > determining that it needs CPA_NET_ADMIN to run the DHCP server, and
> > erroring out because it doesn't have it.
> >
> >
> > Simon.
> >
> >
> > On 19/02/2024 15:32, Martin Ivičič wrote:
> > > Hello,
> > >
> > > I might have stumbled upon a minor bug in dnsmasq which causes
> > NET_ADMIN
> > > capability being required even if it's actually not needed
> > (according to
> > > provided command line arguments).
> > >
> > > diff --git a/src/dnsmasq.c b/src/dnsmasq.c
> > > index 30fb419..cef42f6 100644
> > > --- a/src/dnsmasq.c
> > > +++ b/src/dnsmasq.c
> > > @@ -313,9 +313,10 @@ int main (int argc, char **argv)
> > > {
> > > dhcp_init();
> > > # ifdef HAVE_LINUX_NETWORK
> > > - if (!option_bool(OPT_NO_PING))
> > > - need_cap_net_raw = 1;
> > > - need_cap_net_admin = 1;
> > > + if (!option_bool(OPT_NO_PING)) {
> > > + need_cap_net_raw = 1;
> > > + need_cap_net_admin = 1;
> > > + }
> > > # endif
> > > }
> > >
> > > Without this patch, with following arguments, dnsmasq ends with
> > > "dnsmasq: process is missing required capability NET_ADMIN"
> > >
> > > src/dnsmasq \
> > > --strict-order \
> > > --bind-interfaces \
> > > --interface=br-mgmt \
> > > --listen-address=10.0.0.254 \
> > > --dhcp-range=10.0.0.1,10.0.0.250 \
> > > --dhcp-authoritative \
> > > --no-ping \
> > > --dhcp-broadcast \
> > > --port=0 \
> > > --conf-file= \
> > > --pid-file=/tmp/dnsmasq.pid \
> > > --dhcp-leasefile=/tmp/dnsmasq.leases \
> > > --dhcp-no-override \
> > > --no-daemon
> > >
> > > After applying the patch dnsmasq starts and runs fine.
> > >
> > > Best regards,
> > > Martin
> > >
> > >
> > > _______________________________________________
> > > Dnsmasq-discuss mailing list
> > > Dnsmasq-discuss@lists.thekelleys.org.uk
> > <mailto:Dnsmasq-discuss@lists.thekelleys.org.uk>
> > >
> >
> https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss <
> https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss>
> >
> >
> > _______________________________________________
> > Dnsmasq-discuss mailing list
> > Dnsmasq-discuss@lists.thekelleys.org.uk
> > <mailto:Dnsmasq-discuss@lists.thekelleys.org.uk>
> >
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