[PATCH] geneve: fix max_mtu setting

[PATCH] geneve: fix max_mtu setting

[Haishuang Yan]

For ipv6+udp+geneve encapsulation data, the max_mtu should subtract
sizeof(ipv6hdr), instead of sizeof(iphdr).

Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
---
 drivers/net/geneve.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index aa61708..c676d23 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1036,12 +1036,17 @@ static netdev_tx_t geneve_xmit(struct sk_buff *skb, struct net_device *dev)
 
 static int __geneve_change_mtu(struct net_device *dev, int new_mtu, bool strict)
 {
+	struct geneve_dev *geneve = netdev_priv(dev);
 	/* The max_mtu calculation does not take account of GENEVE
 	 * options, to avoid excluding potentially valid
 	 * configurations.
 	 */
-	int max_mtu = IP_MAX_MTU - GENEVE_BASE_HLEN - sizeof(struct iphdr)
-		- dev->hard_header_len;
+	int max_mtu = IP_MAX_MTU - GENEVE_BASE_HLEN - dev->hard_header_len;
+
+	if (geneve->remote.sa.sa_family == AF_INET)
+		max_mtu -= sizeof(struct iphdr);
+	else
+		max_mtu -= sizeof(struct ipv6hdr);
 
 	if (new_mtu < 68)
 		return -EINVAL;
-- 
1.8.3.1

Re: [PATCH] geneve: fix max_mtu setting

[严海双]

> On Jun 26, 2016, at 8:35 PM, zhuyj <zyjzyj2000@gmail.com> wrote:
> 
> +       if (geneve->remote.sa.sa_family == AF_INET)
> +               max_mtu -= sizeof(struct iphdr);
> +       else
> +               max_mtu -= sizeof(struct ipv6hdr);
> 
> Sorry, if sa_family is not AF_NET, it is AF_INET6?
> 
> There is a lot of macros in include/linux/socket.h.
> 
> Zhu Yanjun
> 

There are only two enumerations AF_INET and AF_INET6 have been assigned in geneve_newlink:

        if (data[IFLA_GENEVE_REMOTE] && data[IFLA_GENEVE_REMOTE6])
                return -EINVAL;

        if (data[IFLA_GENEVE_REMOTE]) {
                remote.sa.sa_family = AF_INET;
                remote.sin.sin_addr.s_addr =
                        nla_get_in_addr(data[IFLA_GENEVE_REMOTE]);
        }

        if (data[IFLA_GENEVE_REMOTE6]) {
                if (!IS_ENABLED(CONFIG_IPV6))
                        return -EPFNOSUPPORT;

                remote.sa.sa_family = AF_INET6;
                remote.sin6.sin6_addr =
                        nla_get_in6_addr(data[IFLA_GENEVE_REMOTE6]);

                if (ipv6_addr_type(&remote.sin6.sin6_addr) &
                    IPV6_ADDR_LINKLOCAL) {
                        netdev_dbg(dev, "link-local remote is unsupported\n");
                        return -EINVAL;
                }
        }

So I think the else case is for AF_INET6 only.

Re: [PATCH] geneve: fix max_mtu setting

[Jesse Gross]

On Sun, Jun 26, 2016 at 6:13 PM, 严海双 <yanhaishuang@cmss.chinamobile.com> wrote:
>
>> On Jun 26, 2016, at 8:35 PM, zhuyj <zyjzyj2000@gmail.com> wrote:
>>
>> +       if (geneve->remote.sa.sa_family == AF_INET)
>> +               max_mtu -= sizeof(struct iphdr);
>> +       else
>> +               max_mtu -= sizeof(struct ipv6hdr);
>>
>> Sorry, if sa_family is not AF_NET, it is AF_INET6?
>>
>> There is a lot of macros in include/linux/socket.h.
>>
>> Zhu Yanjun
>>
>
> There are only two enumerations AF_INET and AF_INET6 have been assigned in geneve_newlink:

There's actually a third possibility: AF_UNSPEC, which is the default
if neither remote type is specified. This is used by lightweight
tunnels and should be able to work with either IPv4/v6. For the
purposes of the MTU calculation this means that the IPv4 header size
should be used to avoid disallowing potentially valid configurations.

Re: [PATCH] geneve: fix max_mtu setting

[Jesse Gross]

On Mon, Jun 27, 2016 at 6:27 PM, 严海双 <yanhaishuang@cmss.chinamobile.com> wrote:
>
> On Jun 28, 2016, at 12:10 AM, Jesse Gross <jesse@kernel.org> wrote:
>
> On Sun, Jun 26, 2016 at 6:13 PM, Haishuang Yan
> <yanhaishuang@cmss.chinamobile.com> wrote:
>
>
> On Jun 26, 2016, at 8:35 PM, zhuyj <zyjzyj2000@gmail.com> wrote:
>
> +       if (geneve->remote.sa.sa_family == AF_INET)
> +               max_mtu -= sizeof(struct iphdr);
> +       else
> +               max_mtu -= sizeof(struct ipv6hdr);
>
> Sorry, if sa_family is not AF_NET, it is AF_INET6?
>
> There is a lot of macros in include/linux/socket.h.
>
> Zhu Yanjun
>
>
> There are only two enumerations AF_INET and AF_INET6 have been assigned in
> geneve_newlink:
>
>
> There's actually a third possibility: AF_UNSPEC, which is the default
> if neither remote type is specified. This is used by lightweight
> tunnels and should be able to work with either IPv4/v6. For the
> purposes of the MTU calculation this means that the IPv4 header size
> should be used to avoid disallowing potentially valid configurations.
>
>
> Yes, you’re right. Thanks for you advise. I will send a v2 commit like this:
>
>        if (geneve->remote.sa.sa_family == AF_INET6)
>               max_mtu -= sizeof(struct ipv6hdr);
>        else
>               max_mtu -= sizeof(struct iphdr);
>
> Is this ok?

Yes, that looks fine to me.