Comment 0 for bug 1912783

[Impact]
Focal linux 5.4.0-57.63 backported from v5.4.78 upstream stable release the following commit, which broke the build of west-chamber dkms modules on Focal and Bionic for all 5.4 kernels based on this release:

"netfilter: use actual socket sk rather than skb sk when routing harder" (Upstream commit 46d6c5ae953cc0be38efd0e469284df7c4328cf8).

This is the same issue found on xtables-addons (bug 1907109).

[Test case]
Install west-chamber-dkms package.

[Fix]

[Where problems could occur]

-----
Testing failing on:
amd64: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-focal/focal/amd64/w/west-chamber/20210121_172911_d9f41@/log.gz
arm64: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-focal/focal/arm64/w/west-chamber/20210113_011159_54cdf@/log.gz
armhf: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-focal/focal/armhf/w/west-chamber/20210113_010911_54cdf@/log.gz
ppc64el: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-focal/focal/ppc64el/w/west-chamber/20210113_010547_54cdf@/log.gz
s390x: https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-focal/focal/s390x/w/west-chamber/20210113_010347_cc516@/log.gz

Build of the dkms is failing with the following error:

/usr/src/west-chamber-20100405+svn20111107.r124/extensions/xt_CUI.c:106:30: error: passing argument 2 of ‘ip_route_me_harder’ from incompatible pointer type [-Werror=incompatible-pointer-types]
  106 | if (ip_route_me_harder(net, skb, addr_type))
      | ^~~
      | |
      | struct sk_buff *
In file included from ./include/linux/netfilter/x_tables.h:245,
                 from /usr/src/west-chamber-20100405+svn20111107.r124/extensions/xt_CUI.c:19:
./include/linux/netfilter_ipv4.h:19:54: note: expected ‘struct sock *’ but argument is of type ‘struct sk_buff *’
   19 | int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned addr_type);
      |