On Wed, Apr 14, 2021 at 05:23:50PM -0700, Martin KaFai Lau wrote:
> On Wed, Apr 14, 2021 at 08:26:08PM +0800, Hangbin Liu wrote:
> [ ... ]
>
> > +static __always_inline int __bpf_xdp_redirect_map(struct bpf_map *map, u32
> > ifindex,
> > + u64 flags, u64 flag_mask,
> > void *lookup_elem(struct
> > bpf_map *map, u32 key))
> > {
> > struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
> >
> > /* Lower bits of the flags are used as return code on lookup failure */
> > - if (unlikely(flags > XDP_TX))
> > + if (unlikely(flags & ~(BPF_F_ACTION_MASK | flag_mask)))
> > return XDP_ABORTED;
> >
> > ri->tgt_value = lookup_elem(map, ifindex);
> > - if (unlikely(!ri->tgt_value)) {
> > + if (unlikely(!ri->tgt_value) && !(flags & BPF_F_BROADCAST)) {
> > /* If the lookup fails we want to clear out the state in the
> > * redirect_info struct completely, so that if an eBPF program
> > * performs multiple lookups, the last one always takes
> > @@ -1482,13 +1484,21 @@ static __always_inline int
> > __bpf_xdp_redirect_map(struct bpf_map *map, u32 ifind
> > */
> > ri->map_id = INT_MAX; /* Valid map id idr range: [1,INT_MAX[ */
> > ri->map_type = BPF_MAP_TYPE_UNSPEC;
> > - return flags;
> > + return flags & BPF_F_ACTION_MASK;
> > }
> >
> > ri->tgt_index = ifindex;
> > ri->map_id = map->id;
> > ri->map_type = map->map_type;
> >
> > + if (flags & BPF_F_BROADCAST) {
> > + WRITE_ONCE(ri->map, map);
> Why only WRITE_ONCE on ri->map? Is it needed?
I think this is make sure the map pointer assigned to ri->map safely.
which starts from commit f6069b9aa993 ("bpf: fix redirect to map under tail
calls")
>
> > + ri->flags = flags;
> > + } else {
> > + WRITE_ONCE(ri->map, NULL);
> > + ri->flags = 0;
> > + }
> > +
> > return XDP_REDIRECT;
> > }
> >
> [ ... ]
>
> > +int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx,
> > + struct bpf_map *map, bool exclude_ingress)
> > +{
> > + struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
> > + int exclude_ifindex = exclude_ingress ? dev_rx->ifindex : 0;
> > + struct bpf_dtab_netdev *dst, *last_dst = NULL;
> > + struct hlist_head *head;
> > + struct hlist_node *next;
> > + struct xdp_frame *xdpf;
> > + unsigned int i;
> > + int err;
> > +
> > + xdpf = xdp_convert_buff_to_frame(xdp);
> > + if (unlikely(!xdpf))
> > + return -EOVERFLOW;
> > +
> > + if (map->map_type == BPF_MAP_TYPE_DEVMAP) {
> > + for (i = 0; i < map->max_entries; i++) {
> > + dst = READ_ONCE(dtab->netdev_map[i]);
> > + if (!is_valid_dst(dst, xdp, exclude_ifindex))
> > + continue;
> > +
> > + /* we only need n-1 clones; last_dst enqueued below */
> > + if (!last_dst) {
> > + last_dst = dst;
> > + continue;
> > + }
> > +
> > + err = dev_map_enqueue_clone(last_dst, dev_rx, xdpf);
> > + if (err)
> > + return err;
> > +
> > + last_dst = dst;
> > + }
> > + } else { /* BPF_MAP_TYPE_DEVMAP_HASH */
> > + for (i = 0; i < dtab->n_buckets; i++) {
> > + head = dev_map_index_hash(dtab, i);
> > + hlist_for_each_entry_safe(dst, next, head, index_hlist)
> > {
> hmm.... should it be hlist_for_each_entry_rcu() instead?
Ah, makes sense to me. I will fix it.
Thanks
Hangbin
