>> @@ -1242,14 +1241,14 @@ static int erspan_tunnel_init(struct net_device *dev)
>> struct ip_tunnel *tunnel = netdev_priv(dev);
>> int t_hlen;
>>
>> - tunnel->tun_hlen = 8;
>> + tunnel->tun_hlen = ERSPAN_GREHDR_LEN;
>> tunnel->parms.iph.protocol = IPPROTO_GRE;
>> tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen +
>> sizeof(struct erspanhdr);
>> t_hlen = tunnel->hlen + sizeof(struct iphdr);
>>
>> - dev->needed_headroom = LL_MAX_HEADER + t_hlen + 4;
>> - dev->mtu = ETH_DATA_LEN - t_hlen - 4;
>> + dev->needed_headroom = LL_MAX_HEADER + t_hlen;
>> + dev->mtu = ETH_DATA_LEN - t_hlen;
> 1. I guess '+4-4' stuff was copied from __gre_tunnel_init(), I'm thinking
> it may be there for some reason.
>
I traced back to
4565e9919cda ("gre: Setup and TX path for gre/UDP foo-over-udp encapsulation")
and I think '+4-4' is there for GRE base header length.
Since now we do
dev->mtu = ETH_DATA_LEN - t_hlen;
and t_hlen already counts the the gre base header + optional header
len, I think it's not needed.
> 2. 'dev->needed_headroom =' and 'dev->mtu =' are really needed ?
> As I've seen both will be updated in .newlink:
> ipgre_newlink() -> ip_tunnel_newlink() -> ip_tunnel_bind_dev()
>
right, I also find both values gets overwritten by
ip_tunnel_bind_dev() using my test cases. Maybe we can remove them?
Thanks
William
