[PATCH v5 0/2] ip/ip6_gre: Fix GRE tunnels not generating IPv6 link local addresses

[PATCH v5 0/2] ip/ip6_gre: Fix GRE tunnels not generating IPv6 link local addresses

[Thomas Winter]

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 e5dd729460ca and this patch set
aims to resolve these issues.

Thomas Winter (2):
  ip/ip6_gre: Fix changing addr gen mode not generating IPv6 link local
    address
  ip/ip6_gre: Fix non-point-to-point tunnel not generating IPv6 link
    local address

 net/ipv6/addrconf.c | 59 ++++++++++++++++++++++++---------------------
 1 file changed, 32 insertions(+), 27 deletions(-)

-- 
2.39.0

[PATCH v5 1/2] ip/ip6_gre: Fix changing addr gen mode not generating IPv6 link local address

[Thomas Winter]

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.
This issue would also have affected SIT tunnels.

Commit e5dd729460ca changed the code path so that GRE tunnels
generate an IPv6 address based on the tunnel source address.
It also changed the code path so GRE tunnels don't call addrconf_addr_gen
in addrconf_dev_config which is called by addrconf_sysctl_addr_gen_mode
when the IN6_ADDR_GEN_MODE is changed.

This patch aims to fix this issue by moving the code in addrconf_notify
which calls the addr gen for GRE and SIT into a separate function
and calling it in the places that expect the IPv6 address to be
generated.

The previous addrconf_dev_config is renamed to addrconf_eth_config
since it only expected eth type interfaces and follows the
addrconf_gre/sit_config format.

A part of this changes means that the loopback address will be
attempted to be configured when changing addr_gen_mode for lo.
This should not be a problem because the address should exist anyway
and if does already exist then no error is produced.

Fixes: e5dd729460ca ("ip/ip6_gre: use the same logic as SIT interfaces when computing v6LL address")
Signed-off-by: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
---
 net/ipv6/addrconf.c | 49 +++++++++++++++++++++++++--------------------
 1 file changed, 27 insertions(+), 22 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index f7a84a4acffc..f4ba68e096ac 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -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);
 				}
 			}
 		}
-- 
2.39.0

[PATCH v5 2/2] ip/ip6_gre: Fix non-point-to-point tunnel not generating IPv6 link local address

[Thomas Winter]

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 when 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 = 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]) {
-- 
2.39.0

Re: [PATCH v5 1/2] ip/ip6_gre: Fix changing addr gen mode not generating IPv6 link local address

[David Ahern]

On 1/30/23 8:46 PM, Thomas Winter wrote:
> 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.
> This issue would also have affected SIT tunnels.
> 
> Commit e5dd729460ca changed the code path so that GRE tunnels
> generate an IPv6 address based on the tunnel source address.
> It also changed the code path so GRE tunnels don't call addrconf_addr_gen
> in addrconf_dev_config which is called by addrconf_sysctl_addr_gen_mode
> when the IN6_ADDR_GEN_MODE is changed.
> 
> This patch aims to fix this issue by moving the code in addrconf_notify
> which calls the addr gen for GRE and SIT into a separate function
> and calling it in the places that expect the IPv6 address to be
> generated.
> 
> The previous addrconf_dev_config is renamed to addrconf_eth_config
> since it only expected eth type interfaces and follows the
> addrconf_gre/sit_config format.
> 
> A part of this changes means that the loopback address will be
> attempted to be configured when changing addr_gen_mode for lo.
> This should not be a problem because the address should exist anyway
> and if does already exist then no error is produced.
> 
> Fixes: e5dd729460ca ("ip/ip6_gre: use the same logic as SIT interfaces when computing v6LL address")
> Signed-off-by: Thomas Winter <Thomas.Winter@alliedtelesis.co.nz>
> ---
>  net/ipv6/addrconf.c | 49 +++++++++++++++++++++++++--------------------
>  1 file changed, 27 insertions(+), 22 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@kernel.org>

Re: [PATCH v5 0/2] ip/ip6_gre: Fix GRE tunnels not generating IPv6 link local addresses

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 31 Jan 2023 16:46:44 +1300 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [v5,1/2] ip/ip6_gre: Fix changing addr gen mode not generating IPv6 link local address
    https://git.kernel.org/netdev/net/c/23ca0c2c9340
  - [v5,2/2] ip/ip6_gre: Fix non-point-to-point tunnel not generating IPv6 link local address
    https://git.kernel.org/netdev/net/c/30e2291f61f9

You are awesome, thank you!
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