This change adds conntrack lookup helpers using the unstable kfunc call interface for the XDP and TC-BPF hooks. The primary usecase is implementing a synproxy in XDP, see Maxim's patchset [0]. Export get_net_ns_by_id as nf_conntrack_bpf.c needs to call it. This object is only built when CONFIG_DEBUG_INFO_BTF_MODULES is enabled. [0]: https://lore.kernel.org/bpf/20211019144655.3483197-1-maximmi@xxxxxxxxxx Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> --- net/core/net_namespace.c | 1 + net/netfilter/Makefile | 5 + net/netfilter/nf_conntrack_bpf.c | 253 +++++++++++++++++++++++++++++++ 3 files changed, 259 insertions(+) create mode 100644 net/netfilter/nf_conntrack_bpf.c diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index 9b7171c40434..3b471781327f 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -299,6 +299,7 @@ struct net *get_net_ns_by_id(const struct net *net, int id) return peer; } +EXPORT_SYMBOL_GPL(get_net_ns_by_id); /* * setup_net runs the initializers for the network namespace object. diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index aab20e575ecd..39338c957d77 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -14,6 +14,11 @@ nf_conntrack-$(CONFIG_NF_CONNTRACK_LABELS) += nf_conntrack_labels.o nf_conntrack-$(CONFIG_NF_CT_PROTO_DCCP) += nf_conntrack_proto_dccp.o nf_conntrack-$(CONFIG_NF_CT_PROTO_SCTP) += nf_conntrack_proto_sctp.o nf_conntrack-$(CONFIG_NF_CT_PROTO_GRE) += nf_conntrack_proto_gre.o +ifeq ($(CONFIG_NF_CONNTRACK),m) +nf_conntrack-$(CONFIG_DEBUG_INFO_BTF_MODULES) += nf_conntrack_bpf.o +else ifeq ($(CONFIG_NF_CONNTRACK),y) +nf_conntrack-$(CONFIG_DEBUG_INFO_BTF) += nf_conntrack_bpf.o +endif obj-$(CONFIG_NETFILTER) = netfilter.o diff --git a/net/netfilter/nf_conntrack_bpf.c b/net/netfilter/nf_conntrack_bpf.c new file mode 100644 index 000000000000..878d5bf947e1 --- /dev/null +++ b/net/netfilter/nf_conntrack_bpf.c @@ -0,0 +1,253 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Unstable Conntrack Helpers for XDP and TC-BPF hook + * + * These are called from the XDP and SCHED_CLS BPF programs. Note that it is + * allowed to break compatibility for these functions since the interface they + * are exposed through to BPF programs is explicitly unstable. + */ + +#include <linux/bpf.h> +#include <linux/btf.h> +#include <linux/types.h> +#include <linux/btf_ids.h> +#include <linux/net_namespace.h> +#include <net/netfilter/nf_conntrack.h> +#include <net/netfilter/nf_conntrack_core.h> + +/* bpf_ct_opts - Options for CT lookup helpers + * + * Members: + * @netns_id - Specify the network namespace for lookup + * Values: + * BPF_F_CURRENT_NETNS (-1) + * Use namespace associated with ctx (xdp_md, __sk_buff) + * [0, S32_MAX] + * Network Namespace ID + * @error - Out parameter, set for any errors encountered + * Values: + * -EINVAL - Passed NULL for bpf_tuple pointer + * -EINVAL - opts->reserved is not 0 + * -EINVAL - netns_id is less than -1 + * -EINVAL - opts__sz isn't NF_BPF_CT_OPTS_SZ (12) + * -EPROTO - l4proto isn't one of IPPROTO_TCP or IPPROTO_UDP + * -ENONET - No network namespace found for netns_id + * -ENOENT - Conntrack lookup could not find entry for tuple + * -EAFNOSUPPORT - tuple__sz isn't one of sizeof(tuple->ipv4) + * or sizeof(tuple->ipv6) + * @l4proto - Layer 4 protocol + * Values: + * IPPROTO_TCP, IPPROTO_UDP + * @reserved - Reserved member, will be reused for more options in future + * Values: + * 0 + */ +struct bpf_ct_opts { + s32 netns_id; + s32 error; + u8 l4proto; + u8 reserved[3]; +}; + +enum { + NF_BPF_CT_OPTS_SZ = 12, +}; + +static struct nf_conn *__bpf_nf_ct_lookup(struct net *net, + struct bpf_sock_tuple *bpf_tuple, + u32 tuple_len, u8 protonum, + s32 netns_id) +{ + struct nf_conntrack_tuple_hash *hash; + struct nf_conntrack_tuple tuple; + + if (unlikely(protonum != IPPROTO_TCP && protonum != IPPROTO_UDP)) + return ERR_PTR(-EPROTO); + if (unlikely(netns_id < BPF_F_CURRENT_NETNS)) + return ERR_PTR(-EINVAL); + + memset(&tuple, 0, sizeof(tuple)); + switch (tuple_len) { + case sizeof(bpf_tuple->ipv4): + tuple.src.l3num = AF_INET; + tuple.src.u3.ip = bpf_tuple->ipv4.saddr; + tuple.src.u.tcp.port = bpf_tuple->ipv4.sport; + tuple.dst.u3.ip = bpf_tuple->ipv4.daddr; + tuple.dst.u.tcp.port = bpf_tuple->ipv4.dport; + break; + case sizeof(bpf_tuple->ipv6): + tuple.src.l3num = AF_INET6; + memcpy(tuple.src.u3.ip6, bpf_tuple->ipv6.saddr, sizeof(bpf_tuple->ipv6.saddr)); + tuple.src.u.tcp.port = bpf_tuple->ipv6.sport; + memcpy(tuple.dst.u3.ip6, bpf_tuple->ipv6.daddr, sizeof(bpf_tuple->ipv6.daddr)); + tuple.dst.u.tcp.port = bpf_tuple->ipv6.dport; + break; + default: + return ERR_PTR(-EAFNOSUPPORT); + } + + tuple.dst.protonum = protonum; + + if (netns_id >= 0) { + net = get_net_ns_by_id(net, netns_id); + if (unlikely(!net)) + return ERR_PTR(-ENONET); + } + + hash = nf_conntrack_find_get(net, &nf_ct_zone_dflt, &tuple); + if (netns_id >= 0) + put_net(net); + if (!hash) + return ERR_PTR(-ENOENT); + return nf_ct_tuplehash_to_ctrack(hash); +} + +__diag_push(); +__diag_ignore(GCC, 8, "-Wmissing-prototypes", + "Global functions as their definitions will be in nf_conntrack BTF"); + +/* bpf_xdp_ct_lookup - Lookup CT entry for the given tuple, and acquire a + * reference to it + * + * Parameters: + * @xdp_ctx - Pointer to ctx (xdp_md) in XDP program + * Cannot be NULL + * @bpf_tuple - Pointer to memory representing the tuple to look up + * Cannot be NULL + * @tuple__sz - Length of the tuple structure + * Must be one of sizeof(bpf_tuple->ipv4) or + * sizeof(bpf_tuple->ipv6) + * @opts - Additional options for lookup (documented above) + * Cannot be NULL + * @opts__sz - Length of the bpf_ct_opts structure + * Must be NF_BPF_CT_OPTS_SZ (12) + */ +struct nf_conn * +bpf_xdp_ct_lookup(struct xdp_md *xdp_ctx, struct bpf_sock_tuple *bpf_tuple, + u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz) +{ + struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx; + struct net *caller_net; + struct nf_conn *nfct; + + BUILD_BUG_ON(sizeof(struct bpf_ct_opts) != NF_BPF_CT_OPTS_SZ); + + if (!opts) + return NULL; + if (!bpf_tuple || opts->reserved[0] || opts->reserved[1] || + opts->reserved[2] || opts__sz != NF_BPF_CT_OPTS_SZ) { + opts->error = -EINVAL; + return NULL; + } + caller_net = dev_net(ctx->rxq->dev); + nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts->l4proto, + opts->netns_id); + if (IS_ERR(nfct)) { + opts->error = PTR_ERR(nfct); + return NULL; + } + return nfct; +} + +/* bpf_skb_ct_lookup - Lookup CT entry for the given tuple, and acquire a + * reference to it + * + * Parameters: + * @skb_ctx - Pointer to ctx (__sk_buff) in TC program + * Cannot be NULL + * @bpf_tuple - Pointer to memory representing the tuple to look up + * Cannot be NULL + * @tuple__sz - Length of the tuple structure + * Must be one of sizeof(bpf_tuple->ipv4) or + * sizeof(bpf_tuple->ipv6) + * @opts - Additional options for lookup (documented above) + * Cannot be NULL + * @opts__sz - Length of the bpf_ct_opts structure + * Must be NF_BPF_CT_OPTS_SZ (12) + */ +struct nf_conn * +bpf_skb_ct_lookup(struct __sk_buff *skb_ctx, struct bpf_sock_tuple *bpf_tuple, + u32 tuple__sz, struct bpf_ct_opts *opts, u32 opts__sz) +{ + struct sk_buff *skb = (struct sk_buff *)skb_ctx; + struct net *caller_net; + struct nf_conn *nfct; + + BUILD_BUG_ON(sizeof(struct bpf_ct_opts) != NF_BPF_CT_OPTS_SZ); + + if (!opts) + return NULL; + if (!bpf_tuple || opts->reserved[0] || opts->reserved[1] || + opts->reserved[2] || opts__sz != NF_BPF_CT_OPTS_SZ) { + opts->error = -EINVAL; + return NULL; + } + caller_net = skb->dev ? dev_net(skb->dev) : sock_net(skb->sk); + nfct = __bpf_nf_ct_lookup(caller_net, bpf_tuple, tuple__sz, opts->l4proto, + opts->netns_id); + if (IS_ERR(nfct)) { + opts->error = PTR_ERR(nfct); + return NULL; + } + return nfct; +} + +/* bpf_ct_release - Release acquired nf_conn object + * + * This must be invoked for referenced PTR_TO_BTF_ID, and the verifier rejects + * the program if any references remain in the program in all of the explored + * states. + * + * Parameters: + * @nf_conn - Pointer to referenced nf_conn object, obtained using + * bpf_xdp_ct_lookup or bpf_skb_ct_lookup. + */ +void bpf_ct_release(struct nf_conn *nfct) +{ + if (!nfct) + return; + nf_ct_put(nfct); +} + +__diag_pop() + +/* XDP hook allowed kfuncs */ +BTF_KFUNC_SET_START(xdp, check, nf_conntrack) +BTF_ID(func, bpf_xdp_ct_lookup) +BTF_ID(func, bpf_ct_release) +BTF_KFUNC_SET_END(xdp, check, nf_conntrack) + +/* XDP hook acquire kfuncs */ +BTF_KFUNC_SET_START(xdp, acquire, nf_conntrack) +BTF_ID(func, bpf_xdp_ct_lookup) +BTF_KFUNC_SET_END(xdp, acquire, nf_conntrack) + +/* XDP hook release kfuncs */ +BTF_KFUNC_SET_START(xdp, release, nf_conntrack) +BTF_ID(func, bpf_ct_release) +BTF_KFUNC_SET_END(xdp, release, nf_conntrack) + +/* XDP hook 'ret type NULL' kfuncs */ +BTF_KFUNC_SET_START(xdp, ret_null, nf_conntrack) +BTF_ID(func, bpf_xdp_ct_lookup) +BTF_KFUNC_SET_END(xdp, ret_null, nf_conntrack) + +/* TC hook allowed kfuncs */ +BTF_KFUNC_SET_START(tc, check, nf_conntrack) +BTF_ID(func, bpf_skb_ct_lookup) +BTF_ID(func, bpf_ct_release) +BTF_KFUNC_SET_END(tc, check, nf_conntrack) + +/* TC hook acquire kfuncs */ +BTF_KFUNC_SET_START(tc, acquire, nf_conntrack) +BTF_ID(func, bpf_skb_ct_lookup) +BTF_KFUNC_SET_END(tc, acquire, nf_conntrack) + +/* TC hook release kfuncs */ +BTF_KFUNC_SET_START(tc, release, nf_conntrack) +BTF_ID(func, bpf_ct_release) +BTF_KFUNC_SET_END(tc, release, nf_conntrack) + +/* TC hook 'ret type NULL' kfuncs */ +BTF_KFUNC_SET_START(tc, ret_null, nf_conntrack) +BTF_ID(func, bpf_skb_ct_lookup) +BTF_KFUNC_SET_END(tc, ret_null, nf_conntrack) -- 2.34.1
