BPF_FIB_LOOKUP_VLAN resolves a VLAN egress. The reverse is also useful: an XDP program receiving a VLAN-tagged frame on a physical device wants the lookup to behave as if the packet had arrived on the corresponding VLAN subinterface, so iif-based policy routing and VRF table selection use the right ingress.
Add BPF_FIB_LOOKUP_VLAN_INPUT. When set, params->h_vlan_proto and params->h_vlan_TCI are read as an input VLAN tag and the matching VLAN device of params->ifindex is resolved with __vlan_find_dev_deep_rcu(). The device must be up and in the same network namespace as params->ifindex (a VLAN device can be moved to another netns while registered on its parent; receive would deliver into that other namespace, which a lookup here cannot represent). If params->ifindex is itself a VLAN device, its inner (QinQ) subinterface is matched. For a bond or team, a tag on a port matches no device and returns NOT_FWDED; pass the master's ifindex. The lookup then runs with the resolved device as the ingress; params->ifindex itself is not modified on the input side. When the resolved device is enslaved to a VRF, both the full lookup (via the l3mdev rule) and BPF_FIB_LOOKUP_DIRECT (via l3mdev_fib_table_rcu()) select the VRF's table from the resolved ingress. That follows from feeding the resolved device to the flow as the ingress (fl4.flowi4_iif = dev->ifindex), which is what makes l3mdev resolve the VRF master from the subinterface rather than from params->ifindex. The two failure classes get different treatment on purpose. A h_vlan_proto other than 802.1Q/802.1ad is API misuse and returns -EINVAL, since it would otherwise reach the WARN in vlan_proto_idx() with a program-controlled value. An unmatched VID, a device that is down, or one in another namespace is a data outcome and returns BPF_FIB_LKUP_RET_NOT_FWDED, matching the DIRECT path when fib_get_table() finds no table and mirroring real ingress, where the receive path drops such frames. A VID of 0 (a priority tag) is looked up literally and normally fails the same way; receive instead processes such frames untagged, so callers should not set the flag for priority tags. Proceeding on the physical device for any of these would be fail-open for the policy-routing cases above. The h_vlan fields share a union with tbid, so the flag cannot be combined with BPF_FIB_LOOKUP_TBID. It describes ingress, so it also cannot be combined with BPF_FIB_LOOKUP_OUTPUT. Both combinations return -EINVAL; restricting now keeps a later relaxation backward compatible. Combining with BPF_FIB_LOOKUP_VLAN is allowed: the tag is consumed on the ingress side and the egress tag is written on success. Under !CONFIG_VLAN_8021Q the __vlan_find_dev_deep_rcu() stub returns NULL, so every lookup with the flag returns NOT_FWDED, which is correct since no VLAN device can exist. Suggested-by: Toke Høiland-Jørgensen <[email protected]> Signed-off-by: Avinash Duduskar <[email protected]> --- include/uapi/linux/bpf.h | 34 ++++++++++++++- net/core/filter.c | 80 +++++++++++++++++++++++++++++++--- tools/include/uapi/linux/bpf.h | 34 ++++++++++++++- 3 files changed, 141 insertions(+), 7 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index f77aa9472bf1..57e28da3336a 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3552,6 +3552,35 @@ union bpf_attr { * reports the route mtu in *params*->mtu_result, and on * the tc path without tot_len the mtu check runs after * the swap, against the parent device. + * **BPF_FIB_LOOKUP_VLAN_INPUT** + * Treat *params*->h_vlan_proto and *params*->h_vlan_TCI + * as an input VLAN tag (e.g. parsed from the packet) and + * run the lookup as if ingress had happened on the VLAN + * subinterface carrying that tag for *params*->ifindex, + * rather than on *params*->ifindex itself. The VID is the + * low 12 bits of *params*->h_vlan_TCI; + * *params*->h_vlan_proto must be ETH_P_8021Q or + * ETH_P_8021AD in network byte order (any other value + * returns **-EINVAL**). The + * subinterface is the one configured for that tag on + * *params*->ifindex; if *params*->ifindex is itself a + * VLAN device, its inner (QinQ) subinterface is matched. + * For a bond or team, a tag on a port matches no + * device and returns NOT_FWDED; pass the master's + * ifindex. + * If no matching subinterface exists, or it is not up, + * or it was moved to another network namespace, the + * lookup returns **BPF_FIB_LKUP_RET_NOT_FWDED**, + * mirroring real ingress, which drops a frame whose tag + * is unconfigured or whose VLAN device is down. A VID of + * 0 (a priority-tagged frame) is looked up literally like + * any other VID; receive instead processes such frames + * untagged on the device itself, so do not set this flag + * for priority tags. + * Cannot be combined with **BPF_FIB_LOOKUP_TBID** (both + * use the same input fields) or **BPF_FIB_LOOKUP_OUTPUT** + * (this flag is ingress-only); doing so returns + * **-EINVAL**. * * *ctx* is either **struct xdp_md** for XDP programs or * **struct sk_buff** tc cls_act programs. @@ -7348,6 +7377,7 @@ enum { BPF_FIB_LOOKUP_SRC = (1U << 4), BPF_FIB_LOOKUP_MARK = (1U << 5), BPF_FIB_LOOKUP_VLAN = (1U << 6), + BPF_FIB_LOOKUP_VLAN_INPUT = (1U << 7), }; enum { @@ -7416,7 +7446,9 @@ struct bpf_fib_lookup { struct { /* output with BPF_FIB_LOOKUP_VLAN: set from the * resolved egress VLAN device (see the flag); zeroed - * on other successful lookups. + * on other successful lookups. input with + * BPF_FIB_LOOKUP_VLAN_INPUT: the VLAN tag to scope + * the lookup by. */ __be16 h_vlan_proto; __be16 h_vlan_TCI; diff --git a/net/core/filter.c b/net/core/filter.c index b37a12321fba..cfbdd842ce61 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6158,6 +6158,41 @@ static int bpf_fib_set_fwd_params(struct net_device *dev, return 0; } + +/* With BPF_FIB_LOOKUP_VLAN_INPUT the caller passes the packet's VLAN tag in + * params->h_vlan_proto and params->h_vlan_TCI; the lookup is done as if + * ingress had happened on the matching VLAN subinterface of *dev. Resolve + * it and store it in *dev. params is not modified. + * + * A protocol other than 802.1Q/802.1AD is API misuse (it would otherwise + * reach the WARN in vlan_proto_idx()), so it is rejected with -EINVAL. An + * unmatched VID, a matching device that is down, or one that was moved + * to another netns (receive would deliver into that netns' stack, which + * a lookup here cannot represent) is a data outcome, reported as + * NOT_FWDED, the same way the DIRECT path reports a missing table. Under + * !CONFIG_VLAN_8021Q __vlan_find_dev_deep_rcu() returns NULL, so every + * call returns NOT_FWDED, which is correct since no subinterface can + * exist. + */ +static int bpf_fib_vlan_input_dev(struct net_device **dev, + const struct bpf_fib_lookup *params) +{ + __be16 proto = params->h_vlan_proto; + struct net_device *vlan_dev; + u16 vid; + + if (proto != htons(ETH_P_8021Q) && proto != htons(ETH_P_8021AD)) + return -EINVAL; + + vid = ntohs(params->h_vlan_TCI) & VLAN_VID_MASK; + vlan_dev = __vlan_find_dev_deep_rcu(*dev, proto, vid); + if (!vlan_dev || !(vlan_dev->flags & IFF_UP) || + !net_eq(dev_net(vlan_dev), dev_net(*dev))) + return BPF_FIB_LKUP_RET_NOT_FWDED; + + *dev = vlan_dev; + return 0; +} #endif #if IS_ENABLED(CONFIG_INET) @@ -6177,6 +6212,12 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (unlikely(!dev)) return -ENODEV; + if (flags & BPF_FIB_LOOKUP_VLAN_INPUT) { + err = bpf_fib_vlan_input_dev(&dev, params); + if (err) + return err; + } + /* verify forwarding is enabled on this interface */ in_dev = __in_dev_get_rcu(dev); if (unlikely(!in_dev || !IN_DEV_FORWARD(in_dev))) @@ -6186,7 +6227,10 @@ static int bpf_ipv4_fib_lookup(struct net *net, struct bpf_fib_lookup *params, fl4.flowi4_iif = 1; fl4.flowi4_oif = params->ifindex; } else { - fl4.flowi4_iif = params->ifindex; + /* dev->ifindex, not params->ifindex: VLAN_INPUT may have + * resolved dev to a subinterface above. + */ + fl4.flowi4_iif = dev->ifindex; fl4.flowi4_oif = 0; } fl4.flowi4_dscp = inet_dsfield_to_dscp(params->tos); @@ -6323,6 +6367,12 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, if (unlikely(!dev)) return -ENODEV; + if (flags & BPF_FIB_LOOKUP_VLAN_INPUT) { + err = bpf_fib_vlan_input_dev(&dev, params); + if (err) + return err; + } + idev = __in6_dev_get_safely(dev); if (unlikely(!idev || !READ_ONCE(idev->cnf.forwarding))) return BPF_FIB_LKUP_RET_FWD_DISABLED; @@ -6331,7 +6381,11 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, fl6.flowi6_iif = 1; oif = fl6.flowi6_oif = params->ifindex; } else { - oif = fl6.flowi6_iif = params->ifindex; + /* dev->ifindex, not params->ifindex: VLAN_INPUT may have + * resolved dev to a subinterface above. + */ + oif = dev->ifindex; + fl6.flowi6_iif = oif; fl6.flowi6_oif = 0; strict = RT6_LOOKUP_F_HAS_SADDR; } @@ -6443,7 +6497,23 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params, #define BPF_FIB_LOOKUP_MASK (BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_OUTPUT | \ BPF_FIB_LOOKUP_SKIP_NEIGH | BPF_FIB_LOOKUP_TBID | \ BPF_FIB_LOOKUP_SRC | BPF_FIB_LOOKUP_MARK | \ - BPF_FIB_LOOKUP_VLAN) + BPF_FIB_LOOKUP_VLAN | BPF_FIB_LOOKUP_VLAN_INPUT) + +static bool bpf_fib_lookup_flags_ok(u32 flags) +{ + if (flags & ~BPF_FIB_LOOKUP_MASK) + return false; + + /* VLAN_INPUT reads h_vlan_proto/h_vlan_TCI, which alias tbid, so it + * cannot be combined with TBID. It is also ingress-only, so it + * cannot be combined with the egress-perspective OUTPUT flag. + */ + if ((flags & BPF_FIB_LOOKUP_VLAN_INPUT) && + (flags & (BPF_FIB_LOOKUP_TBID | BPF_FIB_LOOKUP_OUTPUT))) + return false; + + return true; +} BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx, struct bpf_fib_lookup *, params, int, plen, u32, flags) @@ -6451,7 +6521,7 @@ BPF_CALL_4(bpf_xdp_fib_lookup, struct xdp_buff *, ctx, if (plen < sizeof(*params)) return -EINVAL; - if (flags & ~BPF_FIB_LOOKUP_MASK) + if (!bpf_fib_lookup_flags_ok(flags)) return -EINVAL; switch (params->family) { @@ -6489,7 +6559,7 @@ BPF_CALL_4(bpf_skb_fib_lookup, struct sk_buff *, skb, if (plen < sizeof(*params)) return -EINVAL; - if (flags & ~BPF_FIB_LOOKUP_MASK) + if (!bpf_fib_lookup_flags_ok(flags)) return -EINVAL; if (params->tot_len) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index f77aa9472bf1..57e28da3336a 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -3552,6 +3552,35 @@ union bpf_attr { * reports the route mtu in *params*->mtu_result, and on * the tc path without tot_len the mtu check runs after * the swap, against the parent device. + * **BPF_FIB_LOOKUP_VLAN_INPUT** + * Treat *params*->h_vlan_proto and *params*->h_vlan_TCI + * as an input VLAN tag (e.g. parsed from the packet) and + * run the lookup as if ingress had happened on the VLAN + * subinterface carrying that tag for *params*->ifindex, + * rather than on *params*->ifindex itself. The VID is the + * low 12 bits of *params*->h_vlan_TCI; + * *params*->h_vlan_proto must be ETH_P_8021Q or + * ETH_P_8021AD in network byte order (any other value + * returns **-EINVAL**). The + * subinterface is the one configured for that tag on + * *params*->ifindex; if *params*->ifindex is itself a + * VLAN device, its inner (QinQ) subinterface is matched. + * For a bond or team, a tag on a port matches no + * device and returns NOT_FWDED; pass the master's + * ifindex. + * If no matching subinterface exists, or it is not up, + * or it was moved to another network namespace, the + * lookup returns **BPF_FIB_LKUP_RET_NOT_FWDED**, + * mirroring real ingress, which drops a frame whose tag + * is unconfigured or whose VLAN device is down. A VID of + * 0 (a priority-tagged frame) is looked up literally like + * any other VID; receive instead processes such frames + * untagged on the device itself, so do not set this flag + * for priority tags. + * Cannot be combined with **BPF_FIB_LOOKUP_TBID** (both + * use the same input fields) or **BPF_FIB_LOOKUP_OUTPUT** + * (this flag is ingress-only); doing so returns + * **-EINVAL**. * * *ctx* is either **struct xdp_md** for XDP programs or * **struct sk_buff** tc cls_act programs. @@ -7348,6 +7377,7 @@ enum { BPF_FIB_LOOKUP_SRC = (1U << 4), BPF_FIB_LOOKUP_MARK = (1U << 5), BPF_FIB_LOOKUP_VLAN = (1U << 6), + BPF_FIB_LOOKUP_VLAN_INPUT = (1U << 7), }; enum { @@ -7416,7 +7446,9 @@ struct bpf_fib_lookup { struct { /* output with BPF_FIB_LOOKUP_VLAN: set from the * resolved egress VLAN device (see the flag); zeroed - * on other successful lookups. + * on other successful lookups. input with + * BPF_FIB_LOOKUP_VLAN_INPUT: the VLAN tag to scope + * the lookup by. */ __be16 h_vlan_proto; __be16 h_vlan_TCI; -- 2.54.0
