netdev_upper_dev_link(9)

🦋 netdev_upper_dev_link(9) — Kernel API Manual 🌸

ok so bestie, you found a kernel manpage and it's this one — netdev_upper_dev_link, straight out of the Kernel API Manual (the (9) section, we love a kernel-internals moment 💅). It's giving "one function, whole lotta consequences," and honestly? Iconic. Let's get into it.

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✨ NAME ✨

netdev_upper_dev_link — literally the function that adds a link to the upper device 🫶

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🎀 SYNOPSIS 🎀

int netdev_upper_dev_link (struct net_device *dev, struct net_device *upper_dev, struct netlink_ext_ack *extack);

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💖 ARGUMENTS 💖

• dev — the device. the main character of this call, no cap.
• upper_dev — the new upper device. this is the one being linked above dev, slay.
• extack — netlink extended ack. yes it's a real parameter, yes it's spelled like that 💀

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🔥 DESCRIPTION 🔥

So what does it do? It adds a link to the device which is upper to this one. Like, structurally, hierarchy-wise, the whole vibe check of device stacking 🧚

The caller must hold the RTNL lock. not optional, not a suggestion, not "if you feel like it" — hold the lock, periodt. 🔒

On a failure, you get back a negative errno code. On success, the reference counts get adjusted and the function returns zero. zero = slay, negative = 😭. That's the whole deal, fr fr.

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👑 SEE ALSO 👑

ok this list is long long — like the group chat when someone says "guess what" 💀. Every single one of these, exactly as written:

dev_add_pack(9), __dev_remove_pack(9), dev_remove_pack(9), dev_get_iflink(9), dev_fill_metadata_dst(9), netdev_napi_by_id_lock(9), __dev_get_by_name(9), dev_get_by_name_rcu(9), netdev_get_by_name(9), __dev_get_by_index(9), dev_get_by_index_rcu(9), netdev_get_by_index(9), dev_get_by_napi_id(9), netdev_get_by_index_lock(9), netdev_get_name(9), dev_getbyhwaddr_rcu(9), dev_getbyhwaddr(9), netdev_get_by_flags_rcu(9), dev_valid_name(9), __dev_alloc_name(9), dev_alloc_name(9), dev_get_alias(9), netdev_features_change(9), __netdev_notify_peers(9), netdev_notify_peers(9), dev_disable_gro_hw(9), register_netdevice_notifier(9), unregister_netdevice_notifier(9), register_netdevice_notifier_net(9), unregister_netdevice_notifier_net(9), call_netdevice_notifiers_info(9), call_netdevice_notifiers_info_robust(9), call_netdevice_notifiers(9), call_netdevice_notifiers_mtu(9), dev_forward_skb(9), dev_nit_active_rcu(9), netif_setup_tc(9), netif_set_real_num_rx_queues(9), netif_set_real_num_queues(9), netif_set_tso_max_size(9), netif_set_tso_max_segs(9), netif_inherit_tso_max(9), netif_get_num_default_rss_queues(9), netif_device_detach(9), netif_device_attach(9), dev_loopback_xmit(9), __dev_queue_xmit(9), rps_flow_is_active(9), rps_may_expire_flow(9), __netif_rx(9), netif_rx(9), netdev_is_rx_handler_busy(9), netdev_rx_handler_register(9), netdev_rx_handler_unregister(9), netif_receive_skb_core(9), netif_receive_skb(9), netif_receive_skb_list(9), __napi_schedule(9), napi_schedule_prep(9), __napi_schedule_irqoff(9), netif_threaded_enable(9), netif_queue_set_napi(9), napi_disable(9), napi_enable(9), netdev_has_upper_dev(9), netdev_has_upper_dev_all_rcu(9), netdev_has_any_upper_dev(9), netdev_master_upper_dev_get(9), netdev_has_any_lower_dev(9), netdev_upper_get_next_dev_rcu(9), netdev_lower_get_next_private(9), netdev_lower_get_next_private_rcu(9), netdev_lower_get_next(9), netdev_lower_get_first_private_rcu(9), netdev_master_upper_dev_get_rcu(9), netdev_master_upper_dev_link(9), netdev_upper_dev_unlink(9), netdev_bonding_info_change(9), netdev_get_xmit_slave(9), netdev_sk_get_lowest_dev(9), netdev_lower_state_changed(9), netif_get_flags(9), netif_set_mtu_ext(9), netif_pre_changeaddr_notify(9), dev_get_phys_port_id(9), dev_get_phys_port_name(9), netif_get_port_parent_id(9), netdev_port_same_parent_id(9), netdev_change_proto_down_reason_locked(9), dev_change_xdp_fd(9), dev_index_reserve(9), netdev_update_features(9), netdev_change_features(9), netif_stacked_transfer_operstate(9), register_netdevice(9), register_netdev(9), netdev_wait_allrefs_any(9), dev_get_stats(9), dev_fetch_sw_netstats(9), dev_get_tstats64(9), netdev_sw_irq_coalesce_default_on(9), alloc_netdev_mqs(9), free_netdev(9), alloc_netdev_dummy(9), synchronize_net(9), unregister_netdevice_queue(9), unregister_netdevice_many(9), unregister_netdev(9), netdev_increment_features(9), netdev_compute_master_upper_features(9), netdev_drivername(9)

Like… that's the whole friend group and their cousins 😭 and also the kernel file ./net/core/dev.c is where the magic lives, iykyk 👑

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ok bye bestie, go hold that RTNL lock 💜 — this page came to you from ./net/core (source), October 2026 (that's the date, yes, future vibes ✨), and it's the netdev_upper_dev_link(9) page, signing off 🎀🦋 slay responsibly 🌈