Re: [PATCH] net:l2tp: Allow MAC to be configured via netlink
From: David Miller <davem@davemloft.net>
Date: 2018-01-18 20:44:57
From: Isaac Lee <redacted> 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 <redacted>
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quoted hunk ↗ jump to hunk
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.