diff options
| author | Gabriel Goller <g.goller@proxmox.com> | 2025-07-22 10:18:45 +0200 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2025-07-25 13:06:19 -0700 |
| commit | f24987ef6959a7efaf79bffd265522c3df18d431 (patch) | |
| tree | 69e5a8eb353caac1921f8a64fec640e7087f785d /Documentation | |
| parent | 9312ee76490df61491fee19b5ce71f71b6de908c (diff) | |
ipv6: add `force_forwarding` sysctl to enable per-interface forwarding
It is currently impossible to enable ipv6 forwarding on a per-interface
basis like in ipv4. To enable forwarding on an ipv6 interface we need to
enable it on all interfaces and disable it on the other interfaces using
a netfilter rule. This is especially cumbersome if you have lots of
interfaces and only want to enable forwarding on a few. According to the
sysctl docs [0] the `net.ipv6.conf.all.forwarding` enables forwarding
for all interfaces, while the interface-specific
`net.ipv6.conf.<interface>.forwarding` configures the interface
Host/Router configuration.
Introduce a new sysctl flag `force_forwarding`, which can be set on every
interface. The ip6_forwarding function will then check if the global
forwarding flag OR the force_forwarding flag is active and forward the
packet.
To preserve backwards-compatibility reset the flag (on all interfaces)
to 0 if the net.ipv6.conf.all.forwarding flag is set to 0.
Add a short selftest that checks if a packet gets forwarded with and
without `force_forwarding`.
[0]: https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt
Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Gabriel Goller <g.goller@proxmox.com>
Link: https://patch.msgid.link/20250722081847.132632-1-g.goller@proxmox.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/networking/ip-sysctl.rst | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/Documentation/networking/ip-sysctl.rst b/Documentation/networking/ip-sysctl.rst index 14700ea77e75..bb620f554598 100644 --- a/Documentation/networking/ip-sysctl.rst +++ b/Documentation/networking/ip-sysctl.rst @@ -2543,8 +2543,8 @@ conf/all/disable_ipv6 - BOOLEAN conf/all/forwarding - BOOLEAN Enable global IPv6 forwarding between all interfaces. - IPv4 and IPv6 work differently here; e.g. netfilter must be used - to control which interfaces may forward packets and which not. + IPv4 and IPv6 work differently here; the ``force_forwarding`` flag must + be used to control which interfaces may forward packets. This also sets all interfaces' Host/Router setting 'forwarding' to the specified value. See below for details. @@ -2561,6 +2561,10 @@ proxy_ndp - BOOLEAN Default: 0 (disabled) +force_forwarding - BOOLEAN + Enable forwarding on this interface only -- regardless of the setting on + ``conf/all/forwarding``. When setting ``conf.all.forwarding`` to 0, + the ``force_forwarding`` flag will be reset on all interfaces. fwmark_reflect - BOOLEAN Controls the fwmark of kernel-generated IPv6 reply packets that are not |