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 --- kernel/bpf/net_namespace.c | 5 +++++ kernel/bpf/syscall.c | 9 +++++++++ kernel/bpf/verifier.c | 13 ++++++++++--- 3 files changed, 24 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c index e9c8e26ac8f2..38b368bccda2 100644 --- a/kernel/bpf/net_namespace.c +++ b/kernel/bpf/net_namespace.c @@ -373,6 +373,8 @@ static int netns_bpf_max_progs(enum netns_bpf_attach_type type) switch (type) { case NETNS_BPF_FLOW_DISSECTOR: return 1; + case NETNS_BPF_SK_LOOKUP: + return 64; default: return 0; } @@ -403,6 +405,9 @@ static int netns_bpf_link_attach(struct net *net, struct bpf_link *link, case NETNS_BPF_FLOW_DISSECTOR: err = flow_dissector_bpf_prog_attach_check(net, link->prog); break; + case NETNS_BPF_SK_LOOKUP: + err = 0; /* nothing to check */ + break; default: err = -EINVAL; break; diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 7ea9dfbebd8c..d07417d17712 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2022,6 +2022,10 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type, default: return -EINVAL; } + case BPF_PROG_TYPE_SK_LOOKUP: + if (expected_attach_type == BPF_SK_LOOKUP) + return 0; + return -EINVAL; case BPF_PROG_TYPE_EXT: if (expected_attach_type) return -EINVAL; @@ -2756,6 +2760,7 @@ static int bpf_prog_attach_check_attach_type(const struct bpf_prog *prog, case BPF_PROG_TYPE_CGROUP_SOCK: case BPF_PROG_TYPE_CGROUP_SOCK_ADDR: case BPF_PROG_TYPE_CGROUP_SOCKOPT: + case BPF_PROG_TYPE_SK_LOOKUP: return attach_type == prog->expected_attach_type ? 0 : -EINVAL; case BPF_PROG_TYPE_CGROUP_SKB: if (!capable(CAP_NET_ADMIN)) @@ -2817,6 +2822,8 @@ attach_type_to_prog_type(enum bpf_attach_type attach_type) return BPF_PROG_TYPE_CGROUP_SOCKOPT; case BPF_TRACE_ITER: return BPF_PROG_TYPE_TRACING; + case BPF_SK_LOOKUP: + return BPF_PROG_TYPE_SK_LOOKUP; default: return BPF_PROG_TYPE_UNSPEC; } @@ -2953,6 +2960,7 @@ static int bpf_prog_query(const union bpf_attr *attr, case BPF_LIRC_MODE2: return lirc_prog_query(attr, uattr); case BPF_FLOW_DISSECTOR: + case BPF_SK_LOOKUP: return netns_bpf_prog_query(attr, uattr); default: return -EINVAL; @@ -3891,6 +3899,7 @@ static int link_create(union bpf_attr *attr) ret = tracing_bpf_link_attach(attr, prog); break; case BPF_PROG_TYPE_FLOW_DISSECTOR: + case BPF_PROG_TYPE_SK_LOOKUP: ret = netns_bpf_link_create(attr, prog); break; default: diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3c1efc9d08fd..9a6703bc3f36 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3878,10 +3878,14 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, } meta->ref_obj_id = reg->ref_obj_id; } - } else if (arg_type == ARG_PTR_TO_SOCKET) { + } else if (arg_type == ARG_PTR_TO_SOCKET || + arg_type == ARG_PTR_TO_SOCKET_OR_NULL) { expected_type = PTR_TO_SOCKET; - if (type != expected_type) - goto err_type; + if (!(register_is_null(reg) && + arg_type == ARG_PTR_TO_SOCKET_OR_NULL)) { + if (type != expected_type) + goto err_type; + } } else if (arg_type == ARG_PTR_TO_BTF_ID) { expected_type = PTR_TO_BTF_ID; if (type != expected_type) @@ -7354,6 +7358,9 @@ static int check_return_code(struct bpf_verifier_env *env) return -ENOTSUPP; } break; + case BPF_PROG_TYPE_SK_LOOKUP: + range = tnum_range(SK_DROP, SK_PASS); + break; case BPF_PROG_TYPE_EXT: /* freplace program can return anything as its return value * depends on the to-be-replaced kernel func or bpf program. -- cgit v1.2.3