[PATCH net] ipv6/addrconf: allow adding multicast addr if IFA_F_MCAUTOJOIN is set

The ip address autojoin is not working for IPv6 as ipv6_add_addr()
will return -EADDRNOTAVAIL when adding a multicast address.

Reported-by: Jianlin Shi <redacted>
Fixes: 93a714d6b53d ("multicast: Extend ip address command to enable multicast group join/leave on")
Signed-off-by: Hangbin Liu <redacted>
---
 net/ipv6/addrconf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index dc73888c7859..ced995f3fec4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c

@@ -1045,7 +1045,8 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg,
 	int err = 0;
 
 	if (addr_type == IPV6_ADDR_ANY ||
-	    addr_type & IPV6_ADDR_MULTICAST ||
+	    (addr_type & IPV6_ADDR_MULTICAST &&
+	     !(cfg->ifa_flags & IFA_F_MCAUTOJOIN)) ||
 	    (!(idev->dev->flags & IFF_LOOPBACK) &&
 	     !netif_is_l3_master(idev->dev) &&
 	     addr_type & IPV6_ADDR_LOOPBACK))

-- 
2.19.2

From: Hangbin Liu <redacted>
Date: Tue, 13 Aug 2019 21:52:32 +0800

The ip address autojoin is not working for IPv6 as ipv6_add_addr()
will return -EADDRNOTAVAIL when adding a multicast address.

Reported-by: Jianlin Shi <redacted>
Fixes: 93a714d6b53d ("multicast: Extend ip address command to enable multicast group join/leave on")
Signed-off-by: Hangbin Liu <redacted>

I don't understand how all of this works and why ipv6_add_addr(), which
seems designed explicitly to exclude multicast addresses, should accept
them and what all of the possible fallout might be from such a change.

Your commit message is way too terse and makes it impossible to evaluate
your change.  Really, a change of this nature should have a couple paragraphs
of text explaining the existing situation, what is wrong with it, how you
are fixing it, and why you are fixing it that way.

Thanks.

In commit 93a714d6b53d ("multicast: Extend ip address command to enable
multicast group join/leave on") we added a new flag IFA_F_MCAUTOJOIN
to make user able to add multicast address on ethernet interface.

This works for IPv4, but not for IPv6. See the inet6_addr_add code.

static int inet6_addr_add()
{
	...
	if (cfg->ifa_flags & IFA_F_MCAUTOJOIN) {
		ipv6_mc_config(net->ipv6.mc_autojoin_sk, true...)
	}

	ifp = ipv6_add_addr(idev, cfg, true, extack); <- always fail with maddr
	if (!IS_ERR(ifp)) {
		...
	} else if (cfg->ifa_flags & IFA_F_MCAUTOJOIN) {
		ipv6_mc_config(net->ipv6.mc_autojoin_sk, false...)
	}
}

But in ipv6_add_addr() it will check the address type and reject multicast
address directly. So this feature is never worked for IPv6.

We should not remove the multicast address check totally in ipv6_add_addr(),
but could accept multicast address only when IFA_F_MCAUTOJOIN flag supplied.

v2: update commit description

Reported-by: Jianlin Shi <redacted>
Fixes: 93a714d6b53d ("multicast: Extend ip address command to enable multicast group join/leave on")
Signed-off-by: Hangbin Liu <redacted>
---
 net/ipv6/addrconf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index dc73888c7859..ced995f3fec4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c

@@ -1045,7 +1045,8 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg,
 	int err = 0;
 
 	if (addr_type == IPV6_ADDR_ANY ||
-	    addr_type & IPV6_ADDR_MULTICAST ||
+	    (addr_type & IPV6_ADDR_MULTICAST &&
+	     !(cfg->ifa_flags & IFA_F_MCAUTOJOIN)) ||
 	    (!(idev->dev->flags & IFF_LOOPBACK) &&
 	     !netif_is_l3_master(idev->dev) &&
 	     addr_type & IPV6_ADDR_LOOPBACK))

-- 
2.19.2

On 8/19/19 10:19 PM, Hangbin Liu wrote:

But in ipv6_add_addr() it will check the address type and reject multicast
address directly. So this feature is never worked for IPv6.

If true, that is really disappointing.

We need to get a functional test script started for various address cases.

From: Hangbin Liu <redacted>
Date: Tue, 20 Aug 2019 10:19:47 +0800

In commit 93a714d6b53d ("multicast: Extend ip address command to enable
multicast group join/leave on") we added a new flag IFA_F_MCAUTOJOIN
to make user able to add multicast address on ethernet interface.

This works for IPv4, but not for IPv6. See the inet6_addr_add code.

static int inet6_addr_add()
{
	...
	if (cfg->ifa_flags & IFA_F_MCAUTOJOIN) {
		ipv6_mc_config(net->ipv6.mc_autojoin_sk, true...)
	}

	ifp = ipv6_add_addr(idev, cfg, true, extack); <- always fail with maddr
	if (!IS_ERR(ifp)) {
		...
	} else if (cfg->ifa_flags & IFA_F_MCAUTOJOIN) {
		ipv6_mc_config(net->ipv6.mc_autojoin_sk, false...)
	}
}

But in ipv6_add_addr() it will check the address type and reject multicast
address directly. So this feature is never worked for IPv6.

We should not remove the multicast address check totally in ipv6_add_addr(),
but could accept multicast address only when IFA_F_MCAUTOJOIN flag supplied.

v2: update commit description

Reported-by: Jianlin Shi <redacted>
Fixes: 93a714d6b53d ("multicast: Extend ip address command to enable multicast group join/leave on")
Signed-off-by: Hangbin Liu <redacted>

Applied and queued up for -stable.

On Mon, Aug 19, 2019 at 10:33:58PM -0400, David Ahern wrote:

On 8/19/19 10:19 PM, Hangbin Liu wrote:

quoted

But in ipv6_add_addr() it will check the address type and reject multicast
address directly. So this feature is never worked for IPv6.

If true, that is really disappointing.

We need to get a functional test script started for various address cases.

Do you mean an `ip addr add` testing for all kinds of address types?

Thanks
Hangbin

On 8/22/19 4:20 AM, Hangbin Liu wrote:

On Mon, Aug 19, 2019 at 10:33:58PM -0400, David Ahern wrote:

quoted

On 8/19/19 10:19 PM, Hangbin Liu wrote:

quoted

But in ipv6_add_addr() it will check the address type and reject multicast
address directly. So this feature is never worked for IPv6.

If true, that is really disappointing.

We need to get a functional test script started for various address cases.

Do you mean an `ip addr add` testing for all kinds of address types?

yes.