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bpf: Fix bpf_redirect_neigh helper api to support supplying nexthop
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Based on the discussion in [0], update the bpf_redirect_neigh() helper to
accept an optional parameter specifying the nexthop information. This makes
it possible to combine bpf_fib_lookup() and bpf_redirect_neigh() without
incurring a duplicate FIB lookup - since the FIB lookup helper will return
the nexthop information even if no neighbour is present, this can simply
be passed on to bpf_redirect_neigh() if bpf_fib_lookup() returns
BPF_FIB_LKUP_RET_NO_NEIGH. Thus fix & extend it before helper API is frozen.

  [0] https://lore.kernel.org/bpf/393e17fc-d187-3a8d-2f0d-a627c7c63fca@iogearbox.net/

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/bpf/160322915615.32199.1187570224032024535.stgit@toke.dk
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Toke Høiland-Jørgensen authored and Daniel Borkmann committed Oct 21, 2020
1 parent c5eb48e commit ba452c9
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Showing 5 changed files with 145 additions and 67 deletions.
9 changes: 9 additions & 0 deletions include/linux/filter.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -607,12 +607,21 @@ struct bpf_skb_data_end {
void *data_end;
};

struct bpf_nh_params {
u32 nh_family;
union {
u32 ipv4_nh;
struct in6_addr ipv6_nh;
};
};

struct bpf_redirect_info {
u32 flags;
u32 tgt_index;
void *tgt_value;
struct bpf_map *map;
u32 kern_flags;
struct bpf_nh_params nh;
};

DECLARE_PER_CPU(struct bpf_redirect_info, bpf_redirect_info);
Expand Down
22 changes: 18 additions & 4 deletions include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3677,15 +3677,19 @@ union bpf_attr {
* Return
* The id is returned or 0 in case the id could not be retrieved.
*
* long bpf_redirect_neigh(u32 ifindex, u64 flags)
* long bpf_redirect_neigh(u32 ifindex, struct bpf_redir_neigh *params, int plen, u64 flags)
* Description
* Redirect the packet to another net device of index *ifindex*
* and fill in L2 addresses from neighboring subsystem. This helper
* is somewhat similar to **bpf_redirect**\ (), except that it
* populates L2 addresses as well, meaning, internally, the helper
* performs a FIB lookup based on the skb's networking header to
* get the address of the next hop and then relies on the neighbor
* lookup for the L2 address of the nexthop.
* relies on the neighbor lookup for the L2 address of the nexthop.
*
* The helper will perform a FIB lookup based on the skb's
* networking header to get the address of the next hop, unless
* this is supplied by the caller in the *params* argument. The
* *plen* argument indicates the len of *params* and should be set
* to 0 if *params* is NULL.
*
* The *flags* argument is reserved and must be 0. The helper is
* currently only supported for tc BPF program types, and enabled
Expand Down Expand Up @@ -4906,6 +4910,16 @@ struct bpf_fib_lookup {
__u8 dmac[6]; /* ETH_ALEN */
};

struct bpf_redir_neigh {
/* network family for lookup (AF_INET, AF_INET6) */
__u32 nh_family;
/* network address of nexthop; skips fib lookup to find gateway */
union {
__be32 ipv4_nh;
__u32 ipv6_nh[4]; /* in6_addr; network order */
};
};

enum bpf_task_fd_type {
BPF_FD_TYPE_RAW_TRACEPOINT, /* tp name */
BPF_FD_TYPE_TRACEPOINT, /* tp name */
Expand Down
158 changes: 99 additions & 59 deletions net/core/filter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2165,12 +2165,12 @@ static int __bpf_redirect(struct sk_buff *skb, struct net_device *dev,
}

#if IS_ENABLED(CONFIG_IPV6)
static int bpf_out_neigh_v6(struct net *net, struct sk_buff *skb)
static int bpf_out_neigh_v6(struct net *net, struct sk_buff *skb,
struct net_device *dev, struct bpf_nh_params *nh)
{
struct dst_entry *dst = skb_dst(skb);
struct net_device *dev = dst->dev;
u32 hh_len = LL_RESERVED_SPACE(dev);
const struct in6_addr *nexthop;
struct dst_entry *dst = NULL;
struct neighbour *neigh;

if (dev_xmit_recursion()) {
Expand All @@ -2196,8 +2196,13 @@ static int bpf_out_neigh_v6(struct net *net, struct sk_buff *skb)
}

rcu_read_lock_bh();
nexthop = rt6_nexthop(container_of(dst, struct rt6_info, dst),
&ipv6_hdr(skb)->daddr);
if (!nh) {
dst = skb_dst(skb);
nexthop = rt6_nexthop(container_of(dst, struct rt6_info, dst),
&ipv6_hdr(skb)->daddr);
} else {
nexthop = &nh->ipv6_nh;
}
neigh = ip_neigh_gw6(dev, nexthop);
if (likely(!IS_ERR(neigh))) {
int ret;
Expand All @@ -2210,36 +2215,43 @@ static int bpf_out_neigh_v6(struct net *net, struct sk_buff *skb)
return ret;
}
rcu_read_unlock_bh();
IP6_INC_STATS(dev_net(dst->dev),
ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
if (dst)
IP6_INC_STATS(dev_net(dst->dev),
ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
out_drop:
kfree_skb(skb);
return -ENETDOWN;
}

static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev)
static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev,
struct bpf_nh_params *nh)
{
const struct ipv6hdr *ip6h = ipv6_hdr(skb);
struct net *net = dev_net(dev);
int err, ret = NET_XMIT_DROP;
struct dst_entry *dst;
struct flowi6 fl6 = {
.flowi6_flags = FLOWI_FLAG_ANYSRC,
.flowi6_mark = skb->mark,
.flowlabel = ip6_flowinfo(ip6h),
.flowi6_oif = dev->ifindex,
.flowi6_proto = ip6h->nexthdr,
.daddr = ip6h->daddr,
.saddr = ip6h->saddr,
};

dst = ipv6_stub->ipv6_dst_lookup_flow(net, NULL, &fl6, NULL);
if (IS_ERR(dst))
goto out_drop;
if (!nh) {
struct dst_entry *dst;
struct flowi6 fl6 = {
.flowi6_flags = FLOWI_FLAG_ANYSRC,
.flowi6_mark = skb->mark,
.flowlabel = ip6_flowinfo(ip6h),
.flowi6_oif = dev->ifindex,
.flowi6_proto = ip6h->nexthdr,
.daddr = ip6h->daddr,
.saddr = ip6h->saddr,
};

dst = ipv6_stub->ipv6_dst_lookup_flow(net, NULL, &fl6, NULL);
if (IS_ERR(dst))
goto out_drop;

skb_dst_set(skb, dst);
skb_dst_set(skb, dst);
} else if (nh->nh_family != AF_INET6) {
goto out_drop;
}

err = bpf_out_neigh_v6(net, skb);
err = bpf_out_neigh_v6(net, skb, dev, nh);
if (unlikely(net_xmit_eval(err)))
dev->stats.tx_errors++;
else
Expand All @@ -2252,19 +2264,18 @@ static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev)
return ret;
}
#else
static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev)
static int __bpf_redirect_neigh_v6(struct sk_buff *skb, struct net_device *dev,
struct bpf_nh_params *nh)
{
kfree_skb(skb);
return NET_XMIT_DROP;
}
#endif /* CONFIG_IPV6 */

#if IS_ENABLED(CONFIG_INET)
static int bpf_out_neigh_v4(struct net *net, struct sk_buff *skb)
static int bpf_out_neigh_v4(struct net *net, struct sk_buff *skb,
struct net_device *dev, struct bpf_nh_params *nh)
{
struct dst_entry *dst = skb_dst(skb);
struct rtable *rt = container_of(dst, struct rtable, dst);
struct net_device *dev = dst->dev;
u32 hh_len = LL_RESERVED_SPACE(dev);
struct neighbour *neigh;
bool is_v6gw = false;
Expand Down Expand Up @@ -2292,7 +2303,21 @@ static int bpf_out_neigh_v4(struct net *net, struct sk_buff *skb)
}

rcu_read_lock_bh();
neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
if (!nh) {
struct dst_entry *dst = skb_dst(skb);
struct rtable *rt = container_of(dst, struct rtable, dst);

neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
} else if (nh->nh_family == AF_INET6) {
neigh = ip_neigh_gw6(dev, &nh->ipv6_nh);
is_v6gw = true;
} else if (nh->nh_family == AF_INET) {
neigh = ip_neigh_gw4(dev, nh->ipv4_nh);
} else {
rcu_read_unlock_bh();
goto out_drop;
}

if (likely(!IS_ERR(neigh))) {
int ret;

Expand All @@ -2309,33 +2334,37 @@ static int bpf_out_neigh_v4(struct net *net, struct sk_buff *skb)
return -ENETDOWN;
}

static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev)
static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev,
struct bpf_nh_params *nh)
{
const struct iphdr *ip4h = ip_hdr(skb);
struct net *net = dev_net(dev);
int err, ret = NET_XMIT_DROP;
struct rtable *rt;
struct flowi4 fl4 = {
.flowi4_flags = FLOWI_FLAG_ANYSRC,
.flowi4_mark = skb->mark,
.flowi4_tos = RT_TOS(ip4h->tos),
.flowi4_oif = dev->ifindex,
.flowi4_proto = ip4h->protocol,
.daddr = ip4h->daddr,
.saddr = ip4h->saddr,
};

rt = ip_route_output_flow(net, &fl4, NULL);
if (IS_ERR(rt))
goto out_drop;
if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
ip_rt_put(rt);
goto out_drop;
}
if (!nh) {
struct flowi4 fl4 = {
.flowi4_flags = FLOWI_FLAG_ANYSRC,
.flowi4_mark = skb->mark,
.flowi4_tos = RT_TOS(ip4h->tos),
.flowi4_oif = dev->ifindex,
.flowi4_proto = ip4h->protocol,
.daddr = ip4h->daddr,
.saddr = ip4h->saddr,
};
struct rtable *rt;

rt = ip_route_output_flow(net, &fl4, NULL);
if (IS_ERR(rt))
goto out_drop;
if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
ip_rt_put(rt);
goto out_drop;
}

skb_dst_set(skb, &rt->dst);
skb_dst_set(skb, &rt->dst);
}

err = bpf_out_neigh_v4(net, skb);
err = bpf_out_neigh_v4(net, skb, dev, nh);
if (unlikely(net_xmit_eval(err)))
dev->stats.tx_errors++;
else
Expand All @@ -2348,14 +2377,16 @@ static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev)
return ret;
}
#else
static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev)
static int __bpf_redirect_neigh_v4(struct sk_buff *skb, struct net_device *dev,
struct bpf_nh_params *nh)
{
kfree_skb(skb);
return NET_XMIT_DROP;
}
#endif /* CONFIG_INET */

static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev)
static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev,
struct bpf_nh_params *nh)
{
struct ethhdr *ethh = eth_hdr(skb);

Expand All @@ -2370,9 +2401,9 @@ static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev)
skb_reset_network_header(skb);

if (skb->protocol == htons(ETH_P_IP))
return __bpf_redirect_neigh_v4(skb, dev);
return __bpf_redirect_neigh_v4(skb, dev, nh);
else if (skb->protocol == htons(ETH_P_IPV6))
return __bpf_redirect_neigh_v6(skb, dev);
return __bpf_redirect_neigh_v6(skb, dev, nh);
out:
kfree_skb(skb);
return -ENOTSUPP;
Expand All @@ -2382,7 +2413,8 @@ static int __bpf_redirect_neigh(struct sk_buff *skb, struct net_device *dev)
enum {
BPF_F_NEIGH = (1ULL << 1),
BPF_F_PEER = (1ULL << 2),
#define BPF_F_REDIRECT_INTERNAL (BPF_F_NEIGH | BPF_F_PEER)
BPF_F_NEXTHOP = (1ULL << 3),
#define BPF_F_REDIRECT_INTERNAL (BPF_F_NEIGH | BPF_F_PEER | BPF_F_NEXTHOP)
};

BPF_CALL_3(bpf_clone_redirect, struct sk_buff *, skb, u32, ifindex, u64, flags)
Expand Down Expand Up @@ -2455,7 +2487,8 @@ int skb_do_redirect(struct sk_buff *skb)
return -EAGAIN;
}
return flags & BPF_F_NEIGH ?
__bpf_redirect_neigh(skb, dev) :
__bpf_redirect_neigh(skb, dev, flags & BPF_F_NEXTHOP ?
&ri->nh : NULL) :
__bpf_redirect(skb, dev, flags);
out_drop:
kfree_skb(skb);
Expand Down Expand Up @@ -2504,16 +2537,21 @@ static const struct bpf_func_proto bpf_redirect_peer_proto = {
.arg2_type = ARG_ANYTHING,
};

BPF_CALL_2(bpf_redirect_neigh, u32, ifindex, u64, flags)
BPF_CALL_4(bpf_redirect_neigh, u32, ifindex, struct bpf_redir_neigh *, params,
int, plen, u64, flags)
{
struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);

if (unlikely(flags))
if (unlikely((plen && plen < sizeof(*params)) || flags))
return TC_ACT_SHOT;

ri->flags = BPF_F_NEIGH;
ri->flags = BPF_F_NEIGH | (plen ? BPF_F_NEXTHOP : 0);
ri->tgt_index = ifindex;

BUILD_BUG_ON(sizeof(struct bpf_redir_neigh) != sizeof(struct bpf_nh_params));
if (plen)
memcpy(&ri->nh, params, sizeof(ri->nh));

return TC_ACT_REDIRECT;
}

Expand All @@ -2522,7 +2560,9 @@ static const struct bpf_func_proto bpf_redirect_neigh_proto = {
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_ANYTHING,
.arg2_type = ARG_ANYTHING,
.arg2_type = ARG_PTR_TO_MEM_OR_NULL,
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
.arg4_type = ARG_ANYTHING,
};

BPF_CALL_2(bpf_msg_apply_bytes, struct sk_msg *, msg, u32, bytes)
Expand Down
1 change: 1 addition & 0 deletions scripts/bpf_helpers_doc.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -453,6 +453,7 @@ class PrinterHelpers(Printer):
'struct bpf_perf_event_data',
'struct bpf_perf_event_value',
'struct bpf_pidns_info',
'struct bpf_redir_neigh',
'struct bpf_sk_lookup',
'struct bpf_sock',
'struct bpf_sock_addr',
Expand Down
22 changes: 18 additions & 4 deletions tools/include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3677,15 +3677,19 @@ union bpf_attr {
* Return
* The id is returned or 0 in case the id could not be retrieved.
*
* long bpf_redirect_neigh(u32 ifindex, u64 flags)
* long bpf_redirect_neigh(u32 ifindex, struct bpf_redir_neigh *params, int plen, u64 flags)
* Description
* Redirect the packet to another net device of index *ifindex*
* and fill in L2 addresses from neighboring subsystem. This helper
* is somewhat similar to **bpf_redirect**\ (), except that it
* populates L2 addresses as well, meaning, internally, the helper
* performs a FIB lookup based on the skb's networking header to
* get the address of the next hop and then relies on the neighbor
* lookup for the L2 address of the nexthop.
* relies on the neighbor lookup for the L2 address of the nexthop.
*
* The helper will perform a FIB lookup based on the skb's
* networking header to get the address of the next hop, unless
* this is supplied by the caller in the *params* argument. The
* *plen* argument indicates the len of *params* and should be set
* to 0 if *params* is NULL.
*
* The *flags* argument is reserved and must be 0. The helper is
* currently only supported for tc BPF program types, and enabled
Expand Down Expand Up @@ -4906,6 +4910,16 @@ struct bpf_fib_lookup {
__u8 dmac[6]; /* ETH_ALEN */
};

struct bpf_redir_neigh {
/* network family for lookup (AF_INET, AF_INET6) */
__u32 nh_family;
/* network address of nexthop; skips fib lookup to find gateway */
union {
__be32 ipv4_nh;
__u32 ipv6_nh[4]; /* in6_addr; network order */
};
};

enum bpf_task_fd_type {
BPF_FD_TYPE_RAW_TRACEPOINT, /* tp name */
BPF_FD_TYPE_TRACEPOINT, /* tp name */
Expand Down

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