1 files changed, 252 insertions, 0 deletions
diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
new file mode 100644
index 000000000000..574972bc7299
--- /dev/null
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Facebook  */
+
+#include <linux/types.h>
+#include <linux/bpf_verifier.h>
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/filter.h>
+#include <net/tcp.h>
+
+static u32 optional_ops[] = {
+	offsetof(struct tcp_congestion_ops, init),
+	offsetof(struct tcp_congestion_ops, release),
+	offsetof(struct tcp_congestion_ops, set_state),
+	offsetof(struct tcp_congestion_ops, cwnd_event),
+	offsetof(struct tcp_congestion_ops, in_ack_event),
+	offsetof(struct tcp_congestion_ops, pkts_acked),
+	offsetof(struct tcp_congestion_ops, min_tso_segs),
+	offsetof(struct tcp_congestion_ops, sndbuf_expand),
+	offsetof(struct tcp_congestion_ops, cong_control),
+};
+
+static u32 unsupported_ops[] = {
+	offsetof(struct tcp_congestion_ops, get_info),
+};
+
+static const struct btf_type *tcp_sock_type;
+static u32 tcp_sock_id, sock_id;
+
+static int bpf_tcp_ca_init(struct btf *btf)
+{
+	s32 type_id;
+
+	type_id = btf_find_by_name_kind(btf, "sock", BTF_KIND_STRUCT);
+	if (type_id < 0)
+		return -EINVAL;
+	sock_id = type_id;
+
+	type_id = btf_find_by_name_kind(btf, "tcp_sock", BTF_KIND_STRUCT);
+	if (type_id < 0)
+		return -EINVAL;
+	tcp_sock_id = type_id;
+	tcp_sock_type = btf_type_by_id(btf, tcp_sock_id);
+
+	return 0;
+}
+
+static bool is_optional(u32 member_offset)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {
+		if (member_offset == optional_ops[i])
+			return true;
+	}
+
+	return false;
+}
+
+static bool is_unsupported(u32 member_offset)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(unsupported_ops); i++) {
+		if (member_offset == unsupported_ops[i])
+			return true;
+	}
+
+	return false;
+}
+
+extern struct btf *btf_vmlinux;
+
+static bool bpf_tcp_ca_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(__u64) * MAX_BPF_FUNC_ARGS)
+		return false;
+	if (type != BPF_READ)
+		return false;
+	if (off % size != 0)
+		return false;
+
+	if (!btf_ctx_access(off, size, type, prog, info))
+		return false;
+
+	if (info->reg_type == PTR_TO_BTF_ID && info->btf_id == sock_id)
+		/* promote it to tcp_sock */
+		info->btf_id = tcp_sock_id;
+
+	return true;
+}
+
+static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
+					const struct btf_type *t, int off,
+					int size, enum bpf_access_type atype,
+					u32 *next_btf_id)
+{
+	size_t end;
+
+	if (atype == BPF_READ)
+		return btf_struct_access(log, t, off, size, atype, next_btf_id);
+
+	if (t != tcp_sock_type) {
+		bpf_log(log, "only read is supported\n");
+		return -EACCES;
+	}
+
+	switch (off) {
+	case bpf_ctx_range(struct inet_connection_sock, icsk_ca_priv):
+		end = offsetofend(struct inet_connection_sock, icsk_ca_priv);
+		break;
+	case offsetof(struct inet_connection_sock, icsk_ack.pending):
+		end = offsetofend(struct inet_connection_sock,
+				  icsk_ack.pending);
+		break;
+	case offsetof(struct tcp_sock, snd_cwnd):
+		end = offsetofend(struct tcp_sock, snd_cwnd);
+		break;
+	case offsetof(struct tcp_sock, snd_cwnd_cnt):
+		end = offsetofend(struct tcp_sock, snd_cwnd_cnt);
+		break;
+	case offsetof(struct tcp_sock, snd_ssthresh):
+		end = offsetofend(struct tcp_sock, snd_ssthresh);
+		break;
+	case offsetof(struct tcp_sock, ecn_flags):
+		end = offsetofend(struct tcp_sock, ecn_flags);
+		break;
+	default:
+		bpf_log(log, "no write support to tcp_sock at off %d\n", off);
+		return -EACCES;
+	}
+
+	if (off + size > end) {
+		bpf_log(log,
+			"write access at off %d with size %d beyond the member of tcp_sock ended at %zu\n",
+			off, size, end);
+		return -EACCES;
+	}
+
+	return NOT_INIT;
+}
+
+BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
+{
+	/* bpf_tcp_ca prog cannot have NULL tp */
+	__tcp_send_ack((struct sock *)tp, rcv_nxt);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
+	.func		= bpf_tcp_send_ack,
+	.gpl_only	= false,
+	/* In case we want to report error later */
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID,
+	.arg2_type	= ARG_ANYTHING,
+	.btf_id		= &tcp_sock_id,
+};
+
+static const struct bpf_func_proto *
+bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
+			  const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_tcp_send_ack:
+		return &bpf_tcp_send_ack_proto;
+	default:
+		return bpf_base_func_proto(func_id);
+	}
+}
+
+static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {
+	.get_func_proto		= bpf_tcp_ca_get_func_proto,
+	.is_valid_access	= bpf_tcp_ca_is_valid_access,
+	.btf_struct_access	= bpf_tcp_ca_btf_struct_access,
+};
+
+static int bpf_tcp_ca_init_member(const struct btf_type *t,
+				  const struct btf_member *member,
+				  void *kdata, const void *udata)
+{
+	const struct tcp_congestion_ops *utcp_ca;
+	struct tcp_congestion_ops *tcp_ca;
+	size_t tcp_ca_name_len;
+	int prog_fd;
+	u32 moff;
+
+	utcp_ca = (const struct tcp_congestion_ops *)udata;
+	tcp_ca = (struct tcp_congestion_ops *)kdata;
+
+	moff = btf_member_bit_offset(t, member) / 8;
+	switch (moff) {
+	case offsetof(struct tcp_congestion_ops, flags):
+		if (utcp_ca->flags & ~TCP_CONG_MASK)
+			return -EINVAL;
+		tcp_ca->flags = utcp_ca->flags;
+		return 1;
+	case offsetof(struct tcp_congestion_ops, name):
+		tcp_ca_name_len = strnlen(utcp_ca->name, sizeof(utcp_ca->name));
+		if (!tcp_ca_name_len ||
+		    tcp_ca_name_len == sizeof(utcp_ca->name))
+			return -EINVAL;
+		if (tcp_ca_find(utcp_ca->name))
+			return -EEXIST;
+		memcpy(tcp_ca->name, utcp_ca->name, sizeof(tcp_ca->name));
+		return 1;
+	}
+
+	if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))
+		return 0;
+
+	/* Ensure bpf_prog is provided for compulsory func ptr */
+	prog_fd = (int)(*(unsigned long *)(udata + moff));
+	if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int bpf_tcp_ca_check_member(const struct btf_type *t,
+				   const struct btf_member *member)
+{
+	if (is_unsupported(btf_member_bit_offset(t, member) / 8))
+		return -ENOTSUPP;
+	return 0;
+}
+
+static int bpf_tcp_ca_reg(void *kdata)
+{
+	return tcp_register_congestion_control(kdata);
+}
+
+static void bpf_tcp_ca_unreg(void *kdata)
+{
+	tcp_unregister_congestion_control(kdata);
+}
+
+/* Avoid sparse warning.  It is only used in bpf_struct_ops.c. */
+extern struct bpf_struct_ops bpf_tcp_congestion_ops;
+
+struct bpf_struct_ops bpf_tcp_congestion_ops = {
+	.verifier_ops = &bpf_tcp_ca_verifier_ops,
+	.reg = bpf_tcp_ca_reg,
+	.unreg = bpf_tcp_ca_unreg,
+	.check_member = bpf_tcp_ca_check_member,
+	.init_member = bpf_tcp_ca_init_member,
+	.init = bpf_tcp_ca_init,
+	.name = "tcp_congestion_ops",
+};