bpf: Allow to use kfunc XDP hints and frags together

There is no fundamental reason, why multi-buffer XDP and XDP kfunc RX hints
cannot coexist in a single program.

Allow those features to be used together by modifying the flags condition
for dev-bound-only programs, segments are still prohibited for fully
offloaded programs, hence additional check.
Suggested-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/CAKH8qBuzgtJj=OKMdsxEkyML36VsAuZpcrsXcyqjdKXSJCBq=Q@mail.gmail.com/Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20230915083914.65538-1-larysa.zaremba@intel.comSigned-off-by: Martin KaFai Lau <martin.lau@kernel.org>

kernel/bpf/offload.c

@@ -232,7 +232,14 @@ int bpf_prog_dev_bound_init(struct bpf_prog *prog, union bpf_attr *attr)
 	    attr->prog_type != BPF_PROG_TYPE_XDP)
 		return -EINVAL;
 
-	if (attr->prog_flags & ~BPF_F_XDP_DEV_BOUND_ONLY)
+	if (attr->prog_flags & ~(BPF_F_XDP_DEV_BOUND_ONLY | BPF_F_XDP_HAS_FRAGS))
+		return -EINVAL;
+
+	/* Frags are allowed only if program is dev-bound-only, but not
+	 * if it is requesting bpf offload.
+	 */
+	if (attr->prog_flags & BPF_F_XDP_HAS_FRAGS &&
+	    !(attr->prog_flags & BPF_F_XDP_DEV_BOUND_ONLY))
 		return -EINVAL;
 
 	if (attr->prog_type == BPF_PROG_TYPE_SCHED_CLS &&