Re: [PATCH net-next v5 01/22] rtnetlink: provide permanent hardware address in RTM_NEWLINK

Jiri Pirko
2019-03-26T10:19:28Z

Mon, Mar 25, 2019 at 06:07:57PM CET, mkubecek@suse.cz wrote:
>Permanent hardware address of a network device was traditionally provided
>via ethtool ioctl interface but as Jiri Pirko pointed out in a review of
>ethtool netlink interface, rtnetlink is much more suitable for it so let's
>add it to the RTM_NEWLINK message.
>
>As permanent address is not modifiable, reject userspace requests
>containing IFLA_PERM_ADDRESS attribute.
>
>Note: we already provide permanent hardware address for bond slaves;
>unfortunately we cannot drop that attribute for backward compatibility
>reasons.
>
>Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
>---
> include/uapi/linux/if_link.h | 1 +
> net/core/rtnetlink.c | 4 ++++
> 2 files changed, 5 insertions(+)
>
>diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
>index 5b225ff63b48..351ef746b8b0 100644
>--- a/include/uapi/linux/if_link.h
>+++ b/include/uapi/linux/if_link.h
>@@ -167,6 +167,7 @@ enum {
> IFLA_NEW_IFINDEX,
> IFLA_MIN_MTU,
> IFLA_MAX_MTU,
>+ IFLA_PERM_ADDRESS,
> __IFLA_MAX
> };
>
>diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>index a51cab95ba64..a72e8f4d777b 100644
>--- a/net/core/rtnetlink.c
>+++ b/net/core/rtnetlink.c
>@@ -1026,6 +1026,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
> + nla_total_size(4) /* IFLA_CARRIER_DOWN_COUNT */
> + nla_total_size(4) /* IFLA_MIN_MTU */
> + nla_total_size(4) /* IFLA_MAX_MTU */
>+ + nla_total_size(MAX_ADDR_LEN) /* IFLA_PERM_ADDRESS */
> + 0;
> }
>
>@@ -1683,6 +1684,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
> nla_put_s32(skb, IFLA_NEW_IFINDEX, new_ifindex) < 0)
> goto nla_put_failure;
>
>+ if (nla_put(skb, IFLA_PERM_ADDRESS, dev->addr_len, dev->perm_addr))
>+ goto nla_put_failure;

I don't think we should put permaddr if driver did not set it. 2
solutions:
1) provide a helper that driver will use to set the perm_addr. This
helper sets a "valid bit". Then you only put IFLA_PERM_ADDRESS
in case the "valid bit" is set.
2) Assuming that no driver would set permaddr to all zeroes,
don't put IFLA_PERM_ADDRESS in case permadd is all zeroes.

>
> rcu_read_lock();
> if (rtnl_fill_link_af(skb, dev, ext_filter_mask))
>@@ -1742,6 +1745,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
> [IFLA_CARRIER_DOWN_COUNT] = { .type = NLA_U32 },
> [IFLA_MIN_MTU] = { .type = NLA_U32 },
> [IFLA_MAX_MTU] = { .type = NLA_U32 },
>+ [IFLA_PERM_ADDRESS] = { .type = NLA_REJECT },
> };
>
> static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
>--
>2.21.0
>