From 97fbf1d106b626b49aa05b23404cd46d4b74d456 Mon Sep 17 00:00:00 2001 From: Alasdair McWilliam Date: Wed, 17 Sep 2025 10:55:42 +0100 Subject: [PATCH] rtnetlink: add needed_{head,tail}room attributes Various network interface types make use of needed_{head,tail}room values to efficiently reserve buffer space for additional encapsulation headers, such as VXLAN, Geneve, IPSec, etc. However, it is not currently possible to query these values in a generic way. Introduce ability to query the needed_{head,tail}room values of a network device via rtnetlink, such that applications that may wish to use these values can do so. For example, Cilium agent iterates over present devices based on user config (direct routing, vxlan, geneve, wireguard etc.) and in future will configure netkit in order to expose the needed_{head,tail}room into K8s pods. See b9ed315d3c4c ("netkit: Allow for configuring needed_{head,tail}room"). Suggested-by: Daniel Borkmann Signed-off-by: Alasdair McWilliam Reviewed-by: Daniel Borkmann Link: https://patch.msgid.link/20250917095543.14039-1-alasdair@mcwilliam.dev Signed-off-by: Jakub Kicinski --- include/uapi/linux/if_link.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h index 7f79af6..67a45f9 100644 --- a/include/uapi/linux/if_link.h +++ b/include/uapi/linux/if_link.h @@ -379,6 +379,8 @@ enum { IFLA_DPLL_PIN, IFLA_MAX_PACING_OFFLOAD_HORIZON, IFLA_NETNS_IMMUTABLE, + IFLA_HEADROOM, + IFLA_TAILROOM, __IFLA_MAX };