Where USE="tools" is in effect, the ebuild should check for IPV6_MULTIPLE_TABLES, in addition to IP_MULTIPLE_TABLES. My kernel .config initially had CONFIG_IPV6 set, but none of its child options. While this may not be an especially common arrangement, it resulted in wg-quick failing with my wireguard configuration until the situation was addressed.
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=291988a63b9a201ff1387c5d276c2718e4ce5071 commit 291988a63b9a201ff1387c5d276c2718e4ce5071 Author: Jason A. Donenfeld <zx2c4@gentoo.org> AuthorDate: 2019-12-28 07:54:38 +0000 Commit: Jason A. Donenfeld <zx2c4@gentoo.org> CommitDate: 2019-12-28 08:04:14 +0000 net-vpn/wireguard-tools: check for IPV6_MULTIPLE_TABLES Closes: https://bugs.gentoo.org/671898 Package-Manager: Portage-2.3.84, Repoman-2.3.20 Signed-off-by: Jason A. Donenfeld <zx2c4@gentoo.org> net-vpn/wireguard-tools/wireguard-tools-1.0.20191226.ebuild | 1 + net-vpn/wireguard-tools/wireguard-tools-9999.ebuild | 1 + 2 files changed, 2 insertions(+)