Merge branch 'ip-ip6_gre-fix-gre-tunnels-not-generating-ipv6-link-local-addresses'

Thomas Winter says:

====================
ip/ip6_gre: Fix GRE tunnels not generating IPv6 link local addresses

For our point-to-point GRE tunnels, they have IN6_ADDR_GEN_MODE_NONE
when they are created then we set IN6_ADDR_GEN_MODE_EUI64 when they
come up to generate the IPv6 link local address for the interface.
Recently we found that they were no longer generating IPv6 addresses.

Also, 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.

These failures were caused by commit e5dd7294 and this patch set
aims to resolve these issues.
====================

Link: https://lore.kernel.org/r/20230131034646.237671-1-Thomas.Winter@alliedtelesis.co.nzSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/addrconf.c

@@ -3127,17 +3127,17 @@ static void add_v4_addrs(struct inet6_dev *idev)
 		offset = sizeof(struct in6_addr) - 4;
 	memcpy(&addr.s6_addr32[3], idev->dev->dev_addr + offset, 4);
 
-	if (idev->dev->flags&IFF_POINTOPOINT) {
+	if (!(idev->dev->flags & IFF_POINTOPOINT) && idev->dev->type == ARPHRD_SIT) {
+		scope = IPV6_ADDR_COMPATv4;
+		plen = 96;
+		pflags |= RTF_NONEXTHOP;
+	} else {
 		if (idev->cnf.addr_gen_mode == IN6_ADDR_GEN_MODE_NONE)
 			return;
 
 		addr.s6_addr32[0] = htonl(0xfe800000);
 		scope = IFA_LINK;
 		plen = 64;
-	} else {
-		scope = IPV6_ADDR_COMPATv4;
-		plen = 96;
-		pflags |= RTF_NONEXTHOP;
 	}
 
 	if (addr.s6_addr32[3]) {
@@ -3447,6 +3447,30 @@ static void addrconf_gre_config(struct net_device *dev)
 }
 #endif
 
+static void addrconf_init_auto_addrs(struct net_device *dev)
+{
+	switch (dev->type) {
+#if IS_ENABLED(CONFIG_IPV6_SIT)
+	case ARPHRD_SIT:
+		addrconf_sit_config(dev);
+		break;
+#endif
+#if IS_ENABLED(CONFIG_NET_IPGRE) || IS_ENABLED(CONFIG_IPV6_GRE)
+	case ARPHRD_IP6GRE:
+	case ARPHRD_IPGRE:
+		addrconf_gre_config(dev);
+		break;
+#endif
+	case ARPHRD_LOOPBACK:
+		init_loopback(dev);
+		break;
+
+	default:
+		addrconf_dev_config(dev);
+		break;
+	}
+}
+
 static int fixup_permanent_addr(struct net *net,
 				struct inet6_dev *idev,
 				struct inet6_ifaddr *ifp)
@@ -3615,26 +3639,7 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
 			run_pending = 1;
 		}
 
-		switch (dev->type) {
-#if IS_ENABLED(CONFIG_IPV6_SIT)
-		case ARPHRD_SIT:
-			addrconf_sit_config(dev);
-			break;
-#endif
-#if IS_ENABLED(CONFIG_NET_IPGRE) || IS_ENABLED(CONFIG_IPV6_GRE)
-		case ARPHRD_IP6GRE:
-		case ARPHRD_IPGRE:
-			addrconf_gre_config(dev);
-			break;
-#endif
-		case ARPHRD_LOOPBACK:
-			init_loopback(dev);
-			break;
-
-		default:
-			addrconf_dev_config(dev);
-			break;
-		}
+		addrconf_init_auto_addrs(dev);
 
 		if (!IS_ERR_OR_NULL(idev)) {
 			if (run_pending)
@@ -6397,7 +6402,7 @@ static int addrconf_sysctl_addr_gen_mode(struct ctl_table *ctl, int write,
 
 			if (idev->cnf.addr_gen_mode != new_val) {
 				idev->cnf.addr_gen_mode = new_val;
-				addrconf_dev_config(idev->dev);
+				addrconf_init_auto_addrs(idev->dev);
 			}
 		} else if (&net->ipv6.devconf_all->addr_gen_mode == ctl->data) {
 			struct net_device *dev;
@@ -6408,7 +6413,7 @@ static int addrconf_sysctl_addr_gen_mode(struct ctl_table *ctl, int write,
 				if (idev &&
 				    idev->cnf.addr_gen_mode != new_val) {
 					idev->cnf.addr_gen_mode = new_val;
-					addrconf_dev_config(idev->dev);
+					addrconf_init_auto_addrs(idev->dev);
 				}
 			}
 		}