6.1-stable review patch. If anyone has any objections, please let me know.
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From: Martin KaFai Lau martin.lau@kernel.org
[ Upstream commit 31de4105f00d64570139bc5494a201b0bd57349f ]
The bpf_fib_lookup() also looks up the neigh table. This was done before bpf_redirect_neigh() was added.
In the use case that does not manage the neigh table and requires bpf_fib_lookup() to lookup a fib to decide if it needs to redirect or not, the bpf prog can depend only on using bpf_redirect_neigh() to lookup the neigh. It also keeps the neigh entries fresh and connected.
This patch adds a bpf_fib_lookup flag, SKIP_NEIGH, to avoid the double neigh lookup when the bpf prog always call bpf_redirect_neigh() to do the neigh lookup. The params->smac output is skipped together when SKIP_NEIGH is set because bpf_redirect_neigh() will figure out the smac also.
Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20230217205515.3583372-1-martin.lau@linux.dev Stable-dep-of: 5baa0433a15e ("neighbour: fix data-races around n->output") Signed-off-by: Sasha Levin sashal@kernel.org --- include/uapi/linux/bpf.h | 6 ++++++ net/core/filter.c | 39 ++++++++++++++++++++++------------ tools/include/uapi/linux/bpf.h | 6 ++++++ 3 files changed, 38 insertions(+), 13 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 53bc487947197..92dbe89dafbf5 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3112,6 +3112,11 @@ union bpf_attr { * **BPF_FIB_LOOKUP_OUTPUT** * Perform lookup from an egress perspective (default is * ingress). + * **BPF_FIB_LOOKUP_SKIP_NEIGH** + * Skip the neighbour table lookup. *params*->dmac + * and *params*->smac will not be set as output. A common + * use case is to call **bpf_redirect_neigh**\ () after + * doing **bpf_fib_lookup**\ (). * * *ctx* is either **struct xdp_md** for XDP programs or * **struct sk_buff** tc cls_act programs. @@ -6678,6 +6683,7 @@ struct bpf_raw_tracepoint_args { enum { BPF_FIB_LOOKUP_DIRECT = (1U << 0), BPF_FIB_LOOKUP_OUTPUT = (1U << 1), + BPF_FIB_LOOKUP_SKIP_NEIGH = (1U << 2), };
enum { diff --git a/net/core/filter.c b/net/core/filter.c index 9fd7c88b5db4e..6ef62d84dcac5 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -5674,12 +5674,8 @@ static const struct bpf_func_proto bpf_skb_get_xfrm_state_proto = { #endif
#if IS_ENABLED(CONFIG_INET) || IS_ENABLED(CONFIG_IPV6) -static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params, - const struct neighbour *neigh, - const struct net_device *dev, u32 mtu) +static int bpf_fib_set_fwd_params(struct bpf_fib_lookup *params, u32 mtu) { - memcpy(params->dmac, neigh->ha, ETH_ALEN); - memcpy(params->smac, dev->dev_addr, ETH_ALEN); params->h_vlan_TCI = 0; params->h_vlan_proto = 0; if (mtu) @@ -5790,21 +5786,29 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (likely(nhc->nhc_gw_family != AF_INET6)) { if (nhc->nhc_gw_family) params->ipv4_dst = nhc->nhc_gw.ipv4; - - neigh = __ipv4_neigh_lookup_noref(dev, - (__force u32)params->ipv4_dst); } else { struct in6_addr *dst = (struct in6_addr *)params->ipv6_dst;
params->family = AF_INET6; *dst = nhc->nhc_gw.ipv6; - neigh = __ipv6_neigh_lookup_noref_stub(dev, dst); }
+ if (flags & BPF_FIB_LOOKUP_SKIP_NEIGH) + goto set_fwd_params; + + if (likely(nhc->nhc_gw_family != AF_INET6)) + neigh = __ipv4_neigh_lookup_noref(dev, + (__force u32)params->ipv4_dst); + else + neigh = __ipv6_neigh_lookup_noref_stub(dev, params->ipv6_dst); + if (!neigh || !(neigh->nud_state & NUD_VALID)) return BPF_FIB_LKUP_RET_NO_NEIGH; + memcpy(params->dmac, neigh->ha, ETH_ALEN); + memcpy(params->smac, dev->dev_addr, ETH_ALEN);
- return bpf_fib_set_fwd_params(params, neigh, dev, mtu); +set_fwd_params: + return bpf_fib_set_fwd_params(params, mtu); } #endif
@@ -5912,24 +5916,33 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, params->rt_metric = res.f6i->fib6_metric; params->ifindex = dev->ifindex;
+ if (flags & BPF_FIB_LOOKUP_SKIP_NEIGH) + goto set_fwd_params; + /* xdp and cls_bpf programs are run in RCU-bh so rcu_read_lock_bh is * not needed here. */ neigh = __ipv6_neigh_lookup_noref_stub(dev, dst); if (!neigh || !(neigh->nud_state & NUD_VALID)) return BPF_FIB_LKUP_RET_NO_NEIGH; + memcpy(params->dmac, neigh->ha, ETH_ALEN); + memcpy(params->smac, dev->dev_addr, ETH_ALEN);
- return bpf_fib_set_fwd_params(params, neigh, dev, mtu); +set_fwd_params: + return bpf_fib_set_fwd_params(params, mtu); } #endif
+#define BPF_FIB_LOOKUP_MASK (BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT | \ + BPF_FIB_LOOKUP_SKIP_NEIGH) + BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx, struct bpf_fib_lookup *, params, int, plen, u32, flags) { if (plen < sizeof(*params)) return -EINVAL;
- if (flags & ~(BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT)) + if (flags & ~BPF_FIB_LOOKUP_MASK) return -EINVAL;
switch (params->family) { @@ -5967,7 +5980,7 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, if (plen < sizeof(*params)) return -EINVAL;
- if (flags & ~(BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT)) + if (flags & ~BPF_FIB_LOOKUP_MASK) return -EINVAL;
if (params->tot_len) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 53bc487947197..92dbe89dafbf5 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -3112,6 +3112,11 @@ union bpf_attr { * **BPF_FIB_LOOKUP_OUTPUT** * Perform lookup from an egress perspective (default is * ingress). + * **BPF_FIB_LOOKUP_SKIP_NEIGH** + * Skip the neighbour table lookup. *params*->dmac + * and *params*->smac will not be set as output. A common + * use case is to call **bpf_redirect_neigh**\ () after + * doing **bpf_fib_lookup**\ (). * * *ctx* is either **struct xdp_md** for XDP programs or * **struct sk_buff** tc cls_act programs. @@ -6678,6 +6683,7 @@ struct bpf_raw_tracepoint_args { enum { BPF_FIB_LOOKUP_DIRECT = (1U << 0), BPF_FIB_LOOKUP_OUTPUT = (1U << 1), + BPF_FIB_LOOKUP_SKIP_NEIGH = (1U << 2), };
enum {