| Message ID | 20180117013537.19895-1-isaac.lee@alliedtelesis.co.nz |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | net:l2tp: Allow MAC to be configured via netlink | expand |
From: Isaac Lee <isaac.lee@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.lee@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.
diff --git a/include/uapi/linux/l2tp.h b/include/uapi/linux/l2tp.h index d84ce5c1c9aa..fec15fd774c4 100644 --- a/include/uapi/linux/l2tp.h +++ b/include/uapi/linux/l2tp.h @@ -126,6 +126,7 @@ enum { L2TP_ATTR_IP6_DADDR, /* struct in6_addr */ L2TP_ATTR_UDP_ZERO_CSUM6_TX, /* flag */ L2TP_ATTR_UDP_ZERO_CSUM6_RX, /* flag */ + L2TP_ATTR_HWADDR, /* 6 bytes */ L2TP_ATTR_PAD, __L2TP_ATTR_MAX, }; diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h index 9534e16965cc..730021289ce5 100644 --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -71,6 +71,7 @@ struct l2tp_session_cfg { int mtu; int mru; char *ifname; + unsigned char hwaddr[ETH_ALEN]; }; struct l2tp_session { diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c index 5c366ecfa1cb..0e6ef5379b64 100644 --- a/net/l2tp/l2tp_eth.c +++ b/net/l2tp/l2tp_eth.c @@ -58,7 +58,9 @@ struct l2tp_eth_sess { static int l2tp_eth_dev_init(struct net_device *dev) { - eth_hw_addr_random(dev); + /* Use random MAC only when the interface is created without dev_addr */ + if (!dev->dev_addr || !is_valid_ether_addr(dev->dev_addr)) + eth_hw_addr_random(dev); eth_broadcast_addr(dev->broadcast); netdev_lockdep_set_classes(dev); @@ -309,6 +311,9 @@ static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel, dev->max_mtu = ETH_MAX_MTU; l2tp_eth_adjust_mtu(tunnel, session, dev); + if (is_valid_ether_addr(cfg->hwaddr)) + ether_addr_copy(dev->dev_addr, cfg->hwaddr); + priv = netdev_priv(dev); priv->session = session; 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); + #ifdef CONFIG_MODULES if (l2tp_nl_cmd_ops[cfg.pw_type] == NULL) { genl_unlock();
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.lee@alliedtelesis.co.nz> --- include/uapi/linux/l2tp.h | 1 + net/l2tp/l2tp_core.h | 1 + net/l2tp/l2tp_eth.c | 7 ++++++- net/l2tp/l2tp_netlink.c | 3 +++ 4 files changed, 11 insertions(+), 1 deletion(-)