This reverts commit 43c6d5abacaebf813845934ec8d5e5ee3c431854
(and a small part of 4046d8361c55c80ab8577aea52523b9e6eab0d0c)
It turns out we don't actually need to set the global ip_forward setting.
The only relevant setting is the one on each interface.
What the global toggle actually does is switch forwarding on/off for all
currently present interfaces and change the default for new ones.
That means that by setting the global ip_forward we
- Introduce a race condition, because if the interface with IPForward=yes
is brought up after one with IPForward=no, both will have forwarding
enabled, because the global switch turns it on for all interfaces.
If the other interface comes up first networkd correctly sets forward=0
and it doesn't get overridden.
- Change the forwarding setting for interfaces that networkd is not
configured to touch, even if the user disabled forwarding via sysctl,
either globally or per-interface
As forwarding works fine without this, as long as all relevant interfacest
individually set IPForward=yes: just drop it
This means that non-networkd interfaces use the global default while
networkd interfaces default to off if IPForward isn't given.
---
There were no comments last time[1], maybe it fell through the cracks?
For reference, I have IPForward=yes on br0.network and enp0s25.network.
My /proc/sys/net/ipv4 looks like this and forwarding works fine:
/proc/sys/net/ipv4/ip_forward 0
/proc/sys/net/ipv4/conf/all/forwarding 0
/proc/sys/net/ipv4/conf/br0/forwarding 1
/proc/sys/net/ipv4/conf/default/forwarding 0
/proc/sys/net/ipv4/conf/enp0s25/forwarding 1
...
/proc/sys/net/ipv4/conf/wlp3s0/forwarding 0
before this patch it was:
/proc/sys/net/ipv4/ip_forward 1
/proc/sys/net/ipv4/conf/all/forwarding 1
/proc/sys/net/ipv4/conf/br0/forwarding 1
/proc/sys/net/ipv4/conf/default/forwarding 1
/proc/sys/net/ipv4/conf/enp0s25/forwarding 1
...
/proc/sys/net/ipv4/conf/wlp3s0/forwarding [0 or 1 randomly depending on
if it was faster than br0 and enp0s25 or not]
Even though forwarding is disabled globally via sysctl and wlp3s0 has no
IPForward.
[1] http://lists.freedesktop.org/archives/systemd-devel/2015-April/031352.html
man/systemd.network.xml | 4 +---
src/network/networkd-link.c | 28 +---------------------------
2 files changed, 2 insertions(+), 30 deletions(-)
diff --git a/man/systemd.network.xml b/man/systemd.network.xml
index e4d1820..5504b46 100644
--- a/man/systemd.network.xml
+++ b/man/systemd.network.xml
@@ -373,9 +373,7 @@
globally turned on in the kernel, with the
<filename>net.ipv4.ip_forward</filename> and
<filename>net.ipv4.ip_forward</filename> sysctl
- options. Also, if this option is enabled for at least one
- interface, the global options in the kernel are also enabled
- as necessary, to ensure IP forwarding can take place.</para>
+ options.</para>
</listitem>
</varlistentry>
<varlistentry>
diff --git a/src/network/networkd-link.c b/src/network/networkd-link.c
index 0c6bb65..5d0f199 100644
--- a/src/network/networkd-link.c
+++ b/src/network/networkd-link.c
@@ -1486,39 +1486,13 @@ static int link_enter_join_netdev(Link *link) {
static int link_set_ipv4_forward(Link *link) {
const char *p = NULL;
- bool b;
int r;
- b = link_ipv4_forward_enabled(link);
-
p = strjoina("/proc/sys/net/ipv4/conf/", link->ifname, "/forwarding");
- r = write_string_file_no_create(p, one_zero(b));
+ r = write_string_file_no_create(p,
one_zero(link_ipv4_forward_enabled(link)));
if (r < 0)
log_link_warning_errno(link, r, "Cannot configure IPv4
forwarding for interface %s: %m", link->ifname);
- if (b) {
- _cleanup_free_ char *buf = NULL;
-
- /* If IP forwarding is turned on for this interface,
- * then propagate this to the global setting. Given
- * that turning this on has side-effects on other
- * fields, we'll try to avoid doing this unless
- * necessary, hence check the previous value
- * first. Note that we never turn this option off
- * again, since all interfaces we manage do not do
- * forwarding anyway by default, and ownership rules
- * of this control are so unclear. */
-
- r = read_one_line_file("/proc/sys/net/ipv4/ip_forward", &buf);
- if (r < 0)
- log_link_warning_errno(link, r, "Cannot read
/proc/sys/net/ipv4/ip_forward: %m");
- else if (!streq(buf, "1")) {
- r =
write_string_file_no_create("/proc/sys/net/ipv4/ip_forward", "1");
- if (r < 0)
- log_link_warning_errno(link, r, "Cannot write
/proc/sys/net/ipv4/ip_forward: %m");
- }
- }
-
return 0;
}
--
2.3.3
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