[PATCH net-next 2/3] net: report min and max mtu network device settings

[Stephen Hemminger]

Report the minimum and maximum MTU allowed on a device
via netlink so that it can be displayed by tools like
ip link.

Signed-off-by: Stephen Hemminger <step...@networkplumber.org>
---
 include/uapi/linux/if_link.h | 2 ++
 net/core/rtnetlink.c         | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 01b5069a73a5..1fea3ff73bf6 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -164,6 +164,8 @@ enum {
        IFLA_CARRIER_UP_COUNT,
        IFLA_CARRIER_DOWN_COUNT,
        IFLA_NEW_IFINDEX,
+       IFLA_MIN_MTU,
+       IFLA_MAX_MTU,
        __IFLA_MAX
 };
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 92b6fa5d5f6e..510d4f765a13 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1015,6 +1015,8 @@ static noinline size_t if_nlmsg_size(const struct 
net_device *dev,
               + nla_total_size(4)  /* IFLA_IF_NETNSID */
               + nla_total_size(4)  /* IFLA_CARRIER_UP_COUNT */
               + nla_total_size(4)  /* IFLA_CARRIER_DOWN_COUNT */
+              + nla_total_size(4)  /* IFLA_MIN_MTU */
+              + nla_total_size(4)  /* IFLA_MAX_MTU */
               + 0;
 }
 
@@ -1601,6 +1603,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
                       netif_running(dev) ? dev->operstate : IF_OPER_DOWN) ||
            nla_put_u8(skb, IFLA_LINKMODE, dev->link_mode) ||
            nla_put_u32(skb, IFLA_MTU, dev->mtu) ||
+           nla_put_u32(skb, IFLA_MIN_MTU, dev->min_mtu) ||
+           nla_put_u32(skb, IFLA_MAX_MTU, dev->max_mtu) ||
            nla_put_u32(skb, IFLA_GROUP, dev->group) ||
            nla_put_u32(skb, IFLA_PROMISCUITY, dev->promiscuity) ||
            nla_put_u32(skb, IFLA_NUM_TX_QUEUES, dev->num_tx_queues) ||
@@ -1732,6 +1736,8 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
        [IFLA_IF_NETNSID]       = { .type = NLA_S32 },
        [IFLA_CARRIER_UP_COUNT] = { .type = NLA_U32 },
        [IFLA_CARRIER_DOWN_COUNT] = { .type = NLA_U32 },
+       [IFLA_MIN_MTU]          = { .type = NLA_U32 },
+       [IFLA_MAX_MTU]          = { .type = NLA_U32 },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
-- 
2.18.0