From c8af5cd75e2411d5a5aacf115f59a5ff6b87f3fa Mon Sep 17 00:00:00 2001 From: Toke Høiland-Jørgensen Date: Fri, 28 Jun 2019 11:12:34 +0200 Subject: xskmap: Move non-standard list manipulation to helper MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add a helper in list.h for the non-standard way of clearing a list that is used in xskmap. This makes it easier to reuse it in the other map types, and also makes sure this usage is not forgotten in any list refactorings in the future. Signed-off-by: Toke Høiland-Jørgensen Signed-off-by: Daniel Borkmann --- include/linux/list.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'include') diff --git a/include/linux/list.h b/include/linux/list.h index e951228db4b2..85c92555e31f 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -106,6 +106,20 @@ static inline void __list_del(struct list_head * prev, struct list_head * next) WRITE_ONCE(prev->next, next); } +/* + * Delete a list entry and clear the 'prev' pointer. + * + * This is a special-purpose list clearing method used in the networking code + * for lists allocated as per-cpu, where we don't want to incur the extra + * WRITE_ONCE() overhead of a regular list_del_init(). The code that uses this + * needs to check the node 'prev' pointer instead of calling list_empty(). + */ +static inline void __list_del_clearprev(struct list_head *entry) +{ + __list_del(entry->prev, entry->next); + entry->prev = NULL; +} + /** * list_del - deletes entry from list. * @entry: the element to delete from the list. -- cgit v1.2.3 From 4b55cf290dc6bd3a9e5da26d1ad60e77aa88c8cf Mon Sep 17 00:00:00 2001 From: Toke Høiland-Jørgensen Date: Fri, 28 Jun 2019 11:12:34 +0200 Subject: devmap: Rename ifindex member in bpf_redirect_info MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The bpf_redirect_info struct has an 'ifindex' member which was named back when the redirects could only target egress interfaces. Now that we can also redirect to sockets and CPUs, this is a bit misleading, so rename the member to tgt_index. Reorder the struct members so we can have 'tgt_index' and 'tgt_value' next to each other in a subsequent patch. Signed-off-by: Toke Høiland-Jørgensen Signed-off-by: Daniel Borkmann --- include/linux/filter.h | 2 +- net/core/filter.c | 26 +++++++++++++------------- 2 files changed, 14 insertions(+), 14 deletions(-) (limited to 'include') diff --git a/include/linux/filter.h b/include/linux/filter.h index 340f7d648974..92bd192f7786 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -578,8 +578,8 @@ struct bpf_skb_data_end { }; struct bpf_redirect_info { - u32 ifindex; u32 flags; + u32 tgt_index; struct bpf_map *map; struct bpf_map *map_to_flush; u32 kern_flags; diff --git a/net/core/filter.c b/net/core/filter.c index 1e5fd37e9ab5..b4a062379bb9 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2158,8 +2158,8 @@ BPF_CALL_2(bpf_redirect, u32, ifindex, u64, flags) if (unlikely(flags & ~(BPF_F_INGRESS))) return TC_ACT_SHOT; - ri->ifindex = ifindex; ri->flags = flags; + ri->tgt_index = ifindex; return TC_ACT_REDIRECT; } @@ -2169,8 +2169,8 @@ int skb_do_redirect(struct sk_buff *skb) struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); struct net_device *dev; - dev = dev_get_by_index_rcu(dev_net(skb->dev), ri->ifindex); - ri->ifindex = 0; + dev = dev_get_by_index_rcu(dev_net(skb->dev), ri->tgt_index); + ri->tgt_index = 0; if (unlikely(!dev)) { kfree_skb(skb); return -EINVAL; @@ -3488,11 +3488,11 @@ xdp_do_redirect_slow(struct net_device *dev, struct xdp_buff *xdp, struct bpf_prog *xdp_prog, struct bpf_redirect_info *ri) { struct net_device *fwd; - u32 index = ri->ifindex; + u32 index = ri->tgt_index; int err; fwd = dev_get_by_index_rcu(dev_net(dev), index); - ri->ifindex = 0; + ri->tgt_index = 0; if (unlikely(!fwd)) { err = -EINVAL; goto err; @@ -3604,11 +3604,11 @@ static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp, struct bpf_prog *xdp_prog, struct bpf_map *map, struct bpf_redirect_info *ri) { - u32 index = ri->ifindex; + u32 index = ri->tgt_index; void *fwd = NULL; int err; - ri->ifindex = 0; + ri->tgt_index = 0; WRITE_ONCE(ri->map, NULL); fwd = __xdp_map_lookup_elem(map, index); @@ -3651,11 +3651,11 @@ static int xdp_do_generic_redirect_map(struct net_device *dev, struct bpf_map *map) { struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); - u32 index = ri->ifindex; + u32 index = ri->tgt_index; void *fwd = NULL; int err = 0; - ri->ifindex = 0; + ri->tgt_index = 0; WRITE_ONCE(ri->map, NULL); fwd = __xdp_map_lookup_elem(map, index); @@ -3695,14 +3695,14 @@ int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb, { struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); struct bpf_map *map = READ_ONCE(ri->map); - u32 index = ri->ifindex; + u32 index = ri->tgt_index; struct net_device *fwd; int err = 0; if (map) return xdp_do_generic_redirect_map(dev, skb, xdp, xdp_prog, map); - ri->ifindex = 0; + ri->tgt_index = 0; fwd = dev_get_by_index_rcu(dev_net(dev), index); if (unlikely(!fwd)) { err = -EINVAL; @@ -3730,8 +3730,8 @@ BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, flags) if (unlikely(flags)) return XDP_ABORTED; - ri->ifindex = ifindex; ri->flags = flags; + ri->tgt_index = ifindex; WRITE_ONCE(ri->map, NULL); return XDP_REDIRECT; @@ -3753,8 +3753,8 @@ BPF_CALL_3(bpf_xdp_redirect_map, struct bpf_map *, map, u32, ifindex, if (unlikely(flags)) return XDP_ABORTED; - ri->ifindex = ifindex; ri->flags = flags; + ri->tgt_index = ifindex; WRITE_ONCE(ri->map, map); return XDP_REDIRECT; -- cgit v1.2.3 From 43e74c0267a35d6f5127218054b2d80c7fe801f5 Mon Sep 17 00:00:00 2001 From: Toke Høiland-Jørgensen Date: Fri, 28 Jun 2019 11:12:34 +0200 Subject: bpf_xdp_redirect_map: Perform map lookup in eBPF helper MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The bpf_redirect_map() helper used by XDP programs doesn't return any indication of whether it can successfully redirect to the map index it was given. Instead, BPF programs have to track this themselves, leading to programs using duplicate maps to track which entries are populated in the devmap. This patch fixes this by moving the map lookup into the bpf_redirect_map() helper, which makes it possible to return failure to the eBPF program. The lower bits of the flags argument is used as the return code, which means that existing users who pass a '0' flag argument will get XDP_ABORTED. With this, a BPF program can check the return code from the helper call and react by, for instance, substituting a different redirect. This works for any type of map used for redirect. Signed-off-by: Toke Høiland-Jørgensen Acked-by: Jonathan Lemon Acked-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann --- include/linux/filter.h | 1 + include/trace/events/xdp.h | 5 ++--- include/uapi/linux/bpf.h | 7 +++++-- net/core/filter.c | 32 ++++++++++++++++++-------------- 4 files changed, 26 insertions(+), 19 deletions(-) (limited to 'include') diff --git a/include/linux/filter.h b/include/linux/filter.h index 92bd192f7786..1fe53e78c7e3 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -580,6 +580,7 @@ struct bpf_skb_data_end { struct bpf_redirect_info { u32 flags; u32 tgt_index; + void *tgt_value; struct bpf_map *map; struct bpf_map *map_to_flush; u32 kern_flags; diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h index 81e708c4b513..68899fdc985b 100644 --- a/include/trace/events/xdp.h +++ b/include/trace/events/xdp.h @@ -175,9 +175,8 @@ struct _bpf_dtab_netdev { #endif /* __DEVMAP_OBJ_TYPE */ #define devmap_ifindex(fwd, map) \ - (!fwd ? 0 : \ - ((map->map_type == BPF_MAP_TYPE_DEVMAP) ? \ - ((struct _bpf_dtab_netdev *)fwd)->dev->ifindex : 0)) + ((map->map_type == BPF_MAP_TYPE_DEVMAP) ? \ + ((struct _bpf_dtab_netdev *)fwd)->dev->ifindex : 0) #define _trace_xdp_redirect_map(dev, xdp, fwd, map, idx) \ trace_xdp_redirect_map(dev, xdp, devmap_ifindex(fwd, map), \ diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index a396b516a2b2..cffea1826a1f 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -1571,8 +1571,11 @@ union bpf_attr { * but this is only implemented for native XDP (with driver * support) as of this writing). * - * All values for *flags* are reserved for future usage, and must - * be left at zero. + * The lower two bits of *flags* are used as the return code if + * the map lookup fails. This is so that the return value can be + * one of the XDP program return codes up to XDP_TX, as chosen by + * the caller. Any higher bits in the *flags* argument must be + * unset. * * When used to redirect packets to net devices, this helper * provides a high performance increase over **bpf_redirect**\ (). diff --git a/net/core/filter.c b/net/core/filter.c index b4a062379bb9..4836264f82ee 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -3605,17 +3605,13 @@ static int xdp_do_redirect_map(struct net_device *dev, struct xdp_buff *xdp, struct bpf_redirect_info *ri) { u32 index = ri->tgt_index; - void *fwd = NULL; + void *fwd = ri->tgt_value; int err; ri->tgt_index = 0; + ri->tgt_value = NULL; WRITE_ONCE(ri->map, NULL); - fwd = __xdp_map_lookup_elem(map, index); - if (unlikely(!fwd)) { - err = -EINVAL; - goto err; - } if (ri->map_to_flush && unlikely(ri->map_to_flush != map)) xdp_do_flush_map(); @@ -3652,18 +3648,13 @@ static int xdp_do_generic_redirect_map(struct net_device *dev, { struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); u32 index = ri->tgt_index; - void *fwd = NULL; + void *fwd = ri->tgt_value; int err = 0; ri->tgt_index = 0; + ri->tgt_value = NULL; WRITE_ONCE(ri->map, NULL); - fwd = __xdp_map_lookup_elem(map, index); - if (unlikely(!fwd)) { - err = -EINVAL; - goto err; - } - if (map->map_type == BPF_MAP_TYPE_DEVMAP) { struct bpf_dtab_netdev *dst = fwd; @@ -3732,6 +3723,7 @@ BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, flags) ri->flags = flags; ri->tgt_index = ifindex; + ri->tgt_value = NULL; WRITE_ONCE(ri->map, NULL); return XDP_REDIRECT; @@ -3750,9 +3742,21 @@ BPF_CALL_3(bpf_xdp_redirect_map, struct bpf_map *, map, u32, ifindex, { struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info); - if (unlikely(flags)) + /* Lower bits of the flags are used as return code on lookup failure */ + if (unlikely(flags > XDP_TX)) return XDP_ABORTED; + ri->tgt_value = __xdp_map_lookup_elem(map, ifindex); + if (unlikely(!ri->tgt_value)) { + /* 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 + * precedence. + */ + WRITE_ONCE(ri->map, NULL); + return flags; + } + ri->flags = flags; ri->tgt_index = ifindex; WRITE_ONCE(ri->map, map); -- cgit v1.2.3