Specifically, this sequence:
iptables -N ts-forward
iptables -A ts-forward -m mark --mark 0x10000 -j ACCEPT
iptables -A FORWARD -j ts-forward
doesn't work on Debian-9-using-nftables, but this sequence:
iptables -N ts-forward
iptables -A FORWARD -j ts-forward
iptables -A ts-forward -m mark --mark 0x10000 -j ACCEPT
does work.
I'm sure the reason why is totally fascinating, but it's an old version
of iptables and the bug doesn't seem to exist on modern nftables, so
let's refactor our code to add rules in the always-safe order and
pretend this never happened.
Fixes#401.
Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>
On startup, and when switching into =off and =nodivert, we were
deleting netfilter rules even if we weren't the ones that added them.
In order to avoid interfering with rules added by the sysadmin, we have
to be sure to delete rules only in the case that we added them in the
first place.
Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>
Instead of retrieving the list of chains, or the list of rules in a
chain, just try deleting the ones we don't want and then adding the
ones we do want. An error in flushing/deleting still means the rule
doesn't exist anymore, so there was no need to check for it first.
This avoids the need to parse iptables output, which avoids the need to
ever call iptables -S, which fixes#403, among other things. It's also
much more future proof in case the iptables command line changes.
Unfortunately the iptables go module doesn't properly pass the iptables
command exit code back up when doing .Delete(), so we can't correctly
check the exit code there. (exit code 1 really means the rule didn't
exist, rather than some other weird problem).
Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>
This removes the use of suppress_ifgroup and fwmark "x/y" notation,
which are, among other things, not available in busybox and centos6.
We also use the return codes from the 'ip' program instead of trying to
parse its output.
I also had to remove the previous hack that routed all of 100.64.0.0/10
by default, because that would add the /10 route into the 'main' route
table instead of the new table 88, which is no good. It was a terrible
hack anyway; if we wanted to capture that route, we should have
captured it explicitly as a subnet route, not as part of the addr. Note
however that this change affects all platforms, so hopefully there
won't be any surprises elsewhere.
Fixes#405
Updates #320, #144
Signed-off-by: Avery Pennarun <apenwarr@tailscale.com>
The comment module is compiled out on several embedded systems (and
also gentoo, because netfilter can't go brrrr with comments holding it
back). Attempting to use comments results in a confusing error, and a
non-functional firewall.
Additionally, make the legacy rule cleanup non-fatal, because we *do*
have to probe for the existence of these -m comment rules, and doing
so will error out on these systems.
Signed-off-by: David Anderson <danderson@tailscale.com>
Defensive programming against #368 in environments other than Docker,
e.g. if you try using Tailscale in Alpine Linux directly, sans
container.
Signed-off-by: David Anderson <danderson@tailscale.com>
The iptables package we use doesn't include command output, so we're
left with guessing what went wrong most of the time. This will at
least narrow things down to which operation failed.
Signed-off-by: David Anderson <danderson@tailscale.com>
Instead, pass in only exactly the relevant configuration pieces
that the OS network stack cares about.
Signed-off-by: David Anderson <danderson@tailscale.com>
New logic installs precise filters for subnet routes,
plays nice with other users of netfilter, and lays the
groundwork for fixing routing loops via policy routing.
Signed-off-by: David Anderson <danderson@tailscale.com>
