From: Isaac Lee <isaac....@alliedtelesis.co.nz> Date: Wed, 17 Jan 2018 14:35:37 +1300
> The linux kernel by default uses random MAC address > for l2tp interfaces. However, there are situations > where it is desirable to have a deterministic MAC address. > > A sample scenario would be where the host IP stack is attached > directly to a tunnel hence the "random" address is now propagated > via ARP/ND to the other end of the tunnel. If the device reboots, > a new MAC is used and the communication over the tunnel will be > disrupted until the new MAC address is re-learned by the peer. > Therefore it can be useful to have the mac address the same across > reboots. > > The patch makes the MAC address to be configurable via > netlink so that a userspace program can specify what MAC address to > use at interface creation time in the kernel. > > Signed-off-by: Isaac Lee <isaac....@alliedtelesis.co.nz> ... > diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c > index a1f24fb2be98..dc2933c32121 100644 > --- a/net/l2tp/l2tp_netlink.c > +++ b/net/l2tp/l2tp_netlink.c > @@ -607,6 +607,9 @@ static int l2tp_nl_cmd_session_create(struct sk_buff > *skb, struct genl_info *inf > if (info->attrs[L2TP_ATTR_MRU]) > cfg.mru = nla_get_u16(info->attrs[L2TP_ATTR_MRU]); > > + if (info->attrs[L2TP_ATTR_HWADDR]) > + memcpy(&cfg.hwaddr, nla_data(info->attrs[L2TP_ATTR_HWADDR]), > ETH_ALEN); > + I think you should validate the MAC address here, rather then in l2tp_eth_create(). This way if the address is invalid you can fail the operation and signal an error back to the user. Also, dev->dev_addr can never be NULL in the context of l2tp_eth_dev_init(). As you can see, the existing call to eth_hw_addr_random() writes there unconditionally. Thank you.
