From e9ddbb7707ff5891616240026062b8c1e29864ca Mon Sep 17 00:00:00 2001 From: Jakub Sitnicki Date: Fri, 17 Jul 2020 12:35:23 +0200 Subject: bpf: Introduce SK_LOOKUP program type with a dedicated attach point Add a new program type BPF_PROG_TYPE_SK_LOOKUP with a dedicated attach type BPF_SK_LOOKUP. The new program kind is to be invoked by the transport layer when looking up a listening socket for a new connection request for connection oriented protocols, or when looking up an unconnected socket for a packet for connection-less protocols. When called, SK_LOOKUP BPF program can select a socket that will receive the packet. This serves as a mechanism to overcome the limits of what bind() API allows to express. Two use-cases driving this work are: (1) steer packets destined to an IP range, on fixed port to a socket 192.0.2.0/24, port 80 -> NGINX socket (2) steer packets destined to an IP address, on any port to a socket 198.51.100.1, any port -> L7 proxy socket In its run-time context program receives information about the packet that triggered the socket lookup. Namely IP version, L4 protocol identifier, and address 4-tuple. Context can be further extended to include ingress interface identifier. To select a socket BPF program fetches it from a map holding socket references, like SOCKMAP or SOCKHASH, and calls bpf_sk_assign(ctx, sk, ...) helper to record the selection. Transport layer then uses the selected socket as a result of socket lookup. In its basic form, SK_LOOKUP acts as a filter and hence must return either SK_PASS or SK_DROP. If the program returns with SK_PASS, transport should look for a socket to receive the packet, or use the one selected by the program if available, while SK_DROP informs the transport layer that the lookup should fail. This patch only enables the user to attach an SK_LOOKUP program to a network namespace. Subsequent patches hook it up to run on local delivery path in ipv4 and ipv6 stacks. Suggested-by: Marek Majkowski Signed-off-by: Jakub Sitnicki Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200717103536.397595-3-jakub@cloudflare.com --- net/core/filter.c | 180 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 180 insertions(+) (limited to 'net') diff --git a/net/core/filter.c b/net/core/filter.c index bdd2382e655d..d099436b3ff5 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -9229,6 +9229,186 @@ const struct bpf_verifier_ops sk_reuseport_verifier_ops = { const struct bpf_prog_ops sk_reuseport_prog_ops = { }; + +BPF_CALL_3(bpf_sk_lookup_assign, struct bpf_sk_lookup_kern *, ctx, + struct sock *, sk, u64, flags) +{ + if (unlikely(flags & ~(BPF_SK_LOOKUP_F_REPLACE | + BPF_SK_LOOKUP_F_NO_REUSEPORT))) + return -EINVAL; + if (unlikely(sk && sk_is_refcounted(sk))) + return -ESOCKTNOSUPPORT; /* reject non-RCU freed sockets */ + if (unlikely(sk && sk->sk_state == TCP_ESTABLISHED)) + return -ESOCKTNOSUPPORT; /* reject connected sockets */ + + /* Check if socket is suitable for packet L3/L4 protocol */ + if (sk && sk->sk_protocol != ctx->protocol) + return -EPROTOTYPE; + if (sk && sk->sk_family != ctx->family && + (sk->sk_family == AF_INET || ipv6_only_sock(sk))) + return -EAFNOSUPPORT; + + if (ctx->selected_sk && !(flags & BPF_SK_LOOKUP_F_REPLACE)) + return -EEXIST; + + /* Select socket as lookup result */ + ctx->selected_sk = sk; + ctx->no_reuseport = flags & BPF_SK_LOOKUP_F_NO_REUSEPORT; + return 0; +} + +static const struct bpf_func_proto bpf_sk_lookup_assign_proto = { + .func = bpf_sk_lookup_assign, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_PTR_TO_SOCKET_OR_NULL, + .arg3_type = ARG_ANYTHING, +}; + +static const struct bpf_func_proto * +sk_lookup_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) +{ + switch (func_id) { + case BPF_FUNC_perf_event_output: + return &bpf_event_output_data_proto; + case BPF_FUNC_sk_assign: + return &bpf_sk_lookup_assign_proto; + case BPF_FUNC_sk_release: + return &bpf_sk_release_proto; + default: + return bpf_base_func_proto(func_id); + } +} + +static bool sk_lookup_is_valid_access(int off, int size, + enum bpf_access_type type, + const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + if (off < 0 || off >= sizeof(struct bpf_sk_lookup)) + return false; + if (off % size != 0) + return false; + if (type != BPF_READ) + return false; + + switch (off) { + case offsetof(struct bpf_sk_lookup, sk): + info->reg_type = PTR_TO_SOCKET_OR_NULL; + return size == sizeof(__u64); + + case bpf_ctx_range(struct bpf_sk_lookup, family): + case bpf_ctx_range(struct bpf_sk_lookup, protocol): + case bpf_ctx_range(struct bpf_sk_lookup, remote_ip4): + case bpf_ctx_range(struct bpf_sk_lookup, local_ip4): + case bpf_ctx_range_till(struct bpf_sk_lookup, remote_ip6[0], remote_ip6[3]): + case bpf_ctx_range_till(struct bpf_sk_lookup, local_ip6[0], local_ip6[3]): + case bpf_ctx_range(struct bpf_sk_lookup, remote_port): + case bpf_ctx_range(struct bpf_sk_lookup, local_port): + bpf_ctx_record_field_size(info, sizeof(__u32)); + return bpf_ctx_narrow_access_ok(off, size, sizeof(__u32)); + + default: + return false; + } +} + +static u32 sk_lookup_convert_ctx_access(enum bpf_access_type type, + const struct bpf_insn *si, + struct bpf_insn *insn_buf, + struct bpf_prog *prog, + u32 *target_size) +{ + struct bpf_insn *insn = insn_buf; + + switch (si->off) { + case offsetof(struct bpf_sk_lookup, sk): + *insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg, si->src_reg, + offsetof(struct bpf_sk_lookup_kern, selected_sk)); + break; + + case offsetof(struct bpf_sk_lookup, family): + *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sk_lookup_kern, + family, 2, target_size)); + break; + + case offsetof(struct bpf_sk_lookup, protocol): + *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sk_lookup_kern, + protocol, 2, target_size)); + break; + + case offsetof(struct bpf_sk_lookup, remote_ip4): + *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sk_lookup_kern, + v4.saddr, 4, target_size)); + break; + + case offsetof(struct bpf_sk_lookup, local_ip4): + *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sk_lookup_kern, + v4.daddr, 4, target_size)); + break; + + case bpf_ctx_range_till(struct bpf_sk_lookup, + remote_ip6[0], remote_ip6[3]): { +#if IS_ENABLED(CONFIG_IPV6) + int off = si->off; + + off -= offsetof(struct bpf_sk_lookup, remote_ip6[0]); + off += bpf_target_off(struct in6_addr, s6_addr32[0], 4, target_size); + *insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg, si->src_reg, + offsetof(struct bpf_sk_lookup_kern, v6.saddr)); + *insn++ = BPF_JMP_IMM(BPF_JEQ, si->dst_reg, 0, 1); + *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg, off); +#else + *insn++ = BPF_MOV32_IMM(si->dst_reg, 0); +#endif + break; + } + case bpf_ctx_range_till(struct bpf_sk_lookup, + local_ip6[0], local_ip6[3]): { +#if IS_ENABLED(CONFIG_IPV6) + int off = si->off; + + off -= offsetof(struct bpf_sk_lookup, local_ip6[0]); + off += bpf_target_off(struct in6_addr, s6_addr32[0], 4, target_size); + *insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg, si->src_reg, + offsetof(struct bpf_sk_lookup_kern, v6.daddr)); + *insn++ = BPF_JMP_IMM(BPF_JEQ, si->dst_reg, 0, 1); + *insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg, off); +#else + *insn++ = BPF_MOV32_IMM(si->dst_reg, 0); +#endif + break; + } + case offsetof(struct bpf_sk_lookup, remote_port): + *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sk_lookup_kern, + sport, 2, target_size)); + break; + + case offsetof(struct bpf_sk_lookup, local_port): + *insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->src_reg, + bpf_target_off(struct bpf_sk_lookup_kern, + dport, 2, target_size)); + break; + } + + return insn - insn_buf; +} + +const struct bpf_prog_ops sk_lookup_prog_ops = { +}; + +const struct bpf_verifier_ops sk_lookup_verifier_ops = { + .get_func_proto = sk_lookup_func_proto, + .is_valid_access = sk_lookup_is_valid_access, + .convert_ctx_access = sk_lookup_convert_ctx_access, +}; + #endif /* CONFIG_INET */ DEFINE_BPF_DISPATCHER(xdp) -- cgit v1.2.1