Using routing realms as part of the classifier is quite useful, it can be viewed as a tag for one or multiple routing entries (think of an analogy to net_cls cgroup for processes), set by user space routing daemons or via iproute2 as an indicator for traffic classifiers and later on processed in the eBPF program. Unlike actions, the classifier can inspect device flags and enable netif_keep_dst() if necessary. tc actions don't have that possibility, but in case people know what they are doing, it can be used from there as well (e.g. via devs that must keep dsts by design anyway). If a realm is set, the handler returns the non-zero realm. User space can set the full 32bit realm for the dst.
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| @@ -280,6 +280,13 @@ enum bpf_func_id { · 279 unmodified lines | ||
| 280 | 280 | * Return: TC_ACT_REDIRECT |
| 281 | 281 | */ |
| 282 | 282 | BPF_FUNC_redirect, |
| 283 | + | |
| 284 | + /** | |
| 285 | + * bpf_get_route_realm(skb) - retrieve a dst's tclassid | |
| 286 | + * @skb: pointer to skb | |
| 287 | + * Return: realm if != 0 | |
| 288 | + */ | |
| 289 | + BPF_FUNC_get_route_realm, | |
| 283 | 290 | __BPF_FUNC_MAX_ID, |
| 284 | 291 | }; |
| 285 | 292 | |