From:   Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
To:     davem@davemloft.net, yoshfuji@linux-ipv6.org, dsahern@kernel.org,
        pabeni@redhat.com, edumazet@google.com, kuba@kernel.org,
        a@unstable.cc, netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
Subject: [PATCH v5 2/2] ip/ip6_gre: Fix non-point-to-point tunnel not generating IPv6 link local address
Date:   Tue, 31 Jan 2023 16:46:46 +1300
Message-Id: <20230131034646.237671-3-Thomas.Winter@alliedtelesis.co.nz>
In-Reply-To: <20230131034646.237671-1-Thomas.Winter@alliedtelesis.co.nz>
References: <20230131034646.237671-1-Thomas.Winter@alliedtelesis.co.nz>
MIME-Version: 1.0
Content-Transfer-Encoding: quoted-printable
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We recently found that our non-point-to-point tunnels were not
generating any IPv6 link local address and instead generating an
IPv6 compat address, breaking IPv6 communication on the tunnel.

Previously, addrconf_gre_config always would call addrconf_addr_gen
and generate a EUI64 link local address for the tunnel.
Then commit e5dd729460ca changed the code path so that add_v4_addrs
is called but this only generates a compat IPv6 address for
non-point-to-point tunnels.

I assume the compat address is specifically for SIT tunnels so
have kept that only for SIT - GRE tunnels now always generate link
local addresses.

Fixes: e5dd729460ca ("ip/ip6_gre: use the same logic as SIT interfaces wh=
en computing v6LL address")
Signed-off-by: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
---
 net/ipv6/addrconf.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index f4ba68e096ac..faa47f9ea73a 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3127,17 +3127,17 @@ static void add_v4_addrs(struct inet6_dev *idev)
 		offset =3D sizeof(struct in6_addr) - 4;
 	memcpy(&addr.s6_addr32[3], idev->dev->dev_addr + offset, 4);
=20
-	if (idev->dev->flags&IFF_POINTOPOINT) {
+	if (!(idev->dev->flags & IFF_POINTOPOINT) && idev->dev->type =3D=3D ARP=
HRD_SIT) {
+		scope =3D IPV6_ADDR_COMPATv4;
+		plen =3D 96;
+		pflags |=3D RTF_NONEXTHOP;
+	} else {
 		if (idev->cnf.addr_gen_mode =3D=3D IN6_ADDR_GEN_MODE_NONE)
 			return;
=20
 		addr.s6_addr32[0] =3D htonl(0xfe800000);
 		scope =3D IFA_LINK;
 		plen =3D 64;
-	} else {
-		scope =3D IPV6_ADDR_COMPATv4;
-		plen =3D 96;
-		pflags |=3D RTF_NONEXTHOP;
 	}
=20
 	if (addr.s6_addr32[3]) {
--=20
2.39.0