Revert "gre: Fix IPv6 link-local address generation."

This reverts commit 183185a18ff96751db52a46ccf93fff3a1f42815.

This patch broke net/forwarding/ip6gre_custom_multipath_hash.sh in some
circumstances (https://lore.kernel.org/netdev/Z9RIyKZDNoka53EO@mini-arch/).
Let's revert it while the problem is being investigated.

Fixes: 183185a18ff9 ("gre: Fix IPv6 link-local address generation.")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Link: https://patch.msgid.link/8b1ce738eb15dd841aab9ef888640cab4f6ccfea.1742418408.git.gnault@redhat.com
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 8b6258819dadecc9770b177e3e5181775356b384..ac8cc10765360fe5a8c61d4654308b7559a38c09 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3209,13 +3209,16 @@ static void add_v4_addrs(struct inet6_dev *idev)
        struct in6_addr addr;
        struct net_device *dev;
        struct net *net = dev_net(idev->dev);
-       int scope, plen;
+       int scope, plen, offset = 0;
        u32 pflags = 0;
 
        ASSERT_RTNL();
 
        memset(&addr, 0, sizeof(struct in6_addr));
-       memcpy(&addr.s6_addr32[3], idev->dev->dev_addr, 4);
+       /* in case of IP6GRE the dev_addr is an IPv6 and therefore we use only the last 4 bytes */
+       if (idev->dev->addr_len == sizeof(struct in6_addr))
+               offset = sizeof(struct in6_addr) - 4;
+       memcpy(&addr.s6_addr32[3], idev->dev->dev_addr + offset, 4);
 
        if (!(idev->dev->flags & IFF_POINTOPOINT) && idev->dev->type == ARPHRD_SIT) {
                scope = IPV6_ADDR_COMPATv4;
@@ -3526,13 +3529,7 @@ static void addrconf_gre_config(struct net_device *dev)
                return;
        }
 
-       /* Generate the IPv6 link-local address using addrconf_addr_gen(),
-        * unless we have an IPv4 GRE device not bound to an IP address and
-        * which is in EUI64 mode (as __ipv6_isatap_ifid() would fail in this
-        * case). Such devices fall back to add_v4_addrs() instead.
-        */
-       if (!(dev->type == ARPHRD_IPGRE && *(__be32 *)dev->dev_addr == 0 &&
-             idev->cnf.addr_gen_mode == IN6_ADDR_GEN_MODE_EUI64)) {
+       if (dev->type == ARPHRD_ETHER) {
                addrconf_addr_gen(idev, true);
                return;
        }