Builds with recent glibc would fail with:
../src/network/netdev/fou-tunnel.c: In function ‘config_parse_ip_protocol’:
../src/basic/macro.h:380:9: error: static assertion failed: "IPPROTO_MAX-1 <= UINT8_MAX"
380 | static_assert(expr, #expr)
| ^~~~~~~~~~~~~
../src/network/netdev/fou-tunnel.c:161:9: note: in expansion of macro ‘assert_cc’
161 | assert_cc(IPPROTO_MAX-1 <= UINT8_MAX);
| ^~~~~~~~~
This is because f9ac84f92f151e07586c55e14ed628d493a5929d (present in
glibc-2.31.9000-9.fc33.x86_64) added IPPROTO_MPTCP=262, following
v5.5-rc5-1002-gfaf391c382 in the kernel.
When compiled with -DNDEBUG, we get warnings about set-but-unused variables.
In general, it's not something we care about, but since removing those
variables arguably makes the code nicer, let's just to it in this case.
The option is now called simply "Encapsulation=".
Also, "ignoring" is rather misleading, because we use to to mean that some line
is being ignored. Here the whole tunnel is dropped.
This work add support to generic netlink to sd-netlink.
See https://lwn.net/Articles/208755/
networkd: add support FooOverUDP support to IPIP tunnel netdev
https://lwn.net/Articles/614348/
Example conf:
/lib/systemd/network/1-fou-tunnel.netdev
```
[NetDev]
Name=fou-tun
Kind=fou
[FooOverUDP]
Port=5555
Protocol=4
```
/lib/systemd/network/ipip-tunnel.netdev
```
[NetDev]
Name=ipip-tun
Kind=ipip
[Tunnel]
Independent=true
Local=10.65.208.212
Remote=10.65.208.211
FooOverUDP=true
FOUDestinationPort=5555
```
$ ip -d link show ipip-tun
```
5: ipip-tun@NONE: <POINTOPOINT,NOARP> mtu 1472 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ipip 10.65.208.212 peer 10.65.208.211 promiscuity 0
ipip remote 10.65.208.211 local 10.65.208.212 ttl inherit pmtudisc encap fou encap-sport auto encap-dport 5555 noencap-csum noencap-csum6 noencap-remcsum numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
```
