Re: [PATCH] geneve: fix max_mtu setting

On Jun 26, 2016, at 8:35 PM, zhuyj [off-list ref] 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.

On Sun, Jun 26, 2016 at 6:13 PM, 严海双 [off-list ref] wrote:

quoted

On Jun 26, 2016, at 8:35 PM, zhuyj [off-list ref] 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.