Subject: [PATCH bpf-next v5 04/11] bpf: Support passing args to sock_ops bpf function

From: Lawrence Brakmo <[email-masked]>
Date: Tue, 9 Jan 2018 13:06:57 -0800

Adds support for passing up to 4 arguments to sock_ops bpf functions. It
reusues the reply union, so the bpf_sock_ops structures are not
increased in size.

Signed-off-by: Lawrence Brakmo <[email-masked]>
---
 include/linux/filter.h   |  1 +
 include/net/tcp.h        | 64 ++++++++++++++++++++++++++++++++++++++++++++----
 include/uapi/linux/bpf.h |  5 ++--
 net/ipv4/tcp.c           |  2 +-
 net/ipv4/tcp_nv.c        |  2 +-
 net/ipv4/tcp_output.c    |  2 +-
 6 files changed, 66 insertions(+), 10 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 139a9a3..bbeb781 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1003,6 +1003,7 @@ struct bpf_sock_ops_kern {
 	struct	sock *sk;
 	u32	op;
 	union {
+		u32 args[4];
 		u32 reply;
 		u32 replylong[4];
 	};
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 108d16a..8e9111f 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2005,7 +2005,7 @@ void tcp_cleanup_ulp(struct sock *sk);
  * program loaded).
  */
 #ifdef CONFIG_BPF
-static inline int tcp_call_bpf(struct sock *sk, int op)
+static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
 {
 	struct bpf_sock_ops_kern sock_ops;
 	int ret;
@@ -2018,6 +2018,8 @@ static inline int tcp_call_bpf(struct sock *sk, int op)
 
 	sock_ops.sk = sk;
 	sock_ops.op = op;
+	if (nargs > 0)
+		memcpy(sock_ops.args, args, nargs*sizeof(u32));
 
 	ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
 	if (ret == 0)
@@ -2026,18 +2028,70 @@ static inline int tcp_call_bpf(struct sock *sk, int op)
 		ret = -1;
 	return ret;
 }
+
+static inline int tcp_call_bpf_1arg(struct sock *sk, int op, u32 arg)
+{
+	return tcp_call_bpf(sk, op, 1, &arg);
+}
+
+static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
+{
+	u32 args[2] = {arg1, arg2};
+
+	return tcp_call_bpf(sk, op, 2, args);
+}
+
+static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
+				    u32 arg3)
+{
+	u32 args[3] = {arg1, arg2, arg3};
+
+	return tcp_call_bpf(sk, op, 3, args);
+}
+
+static inline int tcp_call_bpf_4arg(struct sock *sk, int op, u32 arg1, u32 arg2,
+				    u32 arg3, u32 arg4)
+{
+	u32 args[4] = {arg1, arg2, arg3, arg4};
+
+	return tcp_call_bpf(sk, op, 4, args);
+}
+
 #else
-static inline int tcp_call_bpf(struct sock *sk, int op)
+static inline int tcp_call_bpf(struct sock *sk, int op, u32 nargs, u32 *args)
 {
 	return -EPERM;
 }
+
+static inline int tcp_call_bpf_1arg(struct sock *sk, int op, u32 arg)
+{
+	return -EPERM;
+}
+
+static inline int tcp_call_bpf_2arg(struct sock *sk, int op, u32 arg1, u32 arg2)
+{
+	return -EPERM;
+}
+
+static inline int tcp_call_bpf_3arg(struct sock *sk, int op, u32 arg1, u32 arg2,
+	u32 arg3)
+{
+	return -EPERM;
+}
+
+static inline int tcp_call_bpf_4arg(struct sock *sk, int op, u32 arg1, u32 arg2,
+				    u32 arg3, u32 arg4)
+{
+	return -EPERM;
+}
+
 #endif
 
 static inline u32 tcp_timeout_init(struct sock *sk)
 {
 	int timeout;
 
-	timeout = tcp_call_bpf(sk, BPF_SOCK_OPS_TIMEOUT_INIT);
+	timeout = tcp_call_bpf(sk, BPF_SOCK_OPS_TIMEOUT_INIT, 0, NULL);
 
 	if (timeout <= 0)
 		timeout = TCP_TIMEOUT_INIT;
@@ -2048,7 +2102,7 @@ static inline u32 tcp_rwnd_init_bpf(struct sock *sk)
 {
 	int rwnd;
 
-	rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT);
+	rwnd = tcp_call_bpf(sk, BPF_SOCK_OPS_RWND_INIT, 0, NULL);
 
 	if (rwnd < 0)
 		rwnd = 0;
@@ -2057,7 +2111,7 @@ static inline u32 tcp_rwnd_init_bpf(struct sock *sk)
 
 static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
 {
-	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN) == 1);
+	return (tcp_call_bpf(sk, BPF_SOCK_OPS_NEEDS_ECN, 0, NULL) == 1);
 }
 
 #if IS_ENABLED(CONFIG_SMC)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 405317f..94212da 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -948,8 +948,9 @@ struct bpf_map_info {
 struct bpf_sock_ops {
 	__u32 op;
 	union {
-		__u32 reply;
-		__u32 replylong[4];
+		__u32 args[4];		/* Optionally passed to bpf program */
+		__u32 reply;		/* Returned by bpf program	    */
+		__u32 replylong[4];	/* Optionally returned by bpf prog  */
 	};
 	__u32 family;
 	__u32 remote_ip4;	/* Stored in network byte order */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index f68cb33..fcec082 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -463,7 +463,7 @@ void tcp_init_transfer(struct sock *sk, int bpf_op)
 	tcp_mtup_init(sk);
 	icsk->icsk_af_ops->rebuild_header(sk);
 	tcp_init_metrics(sk);
-	tcp_call_bpf(sk, bpf_op);
+	tcp_call_bpf(sk, bpf_op, 0, NULL);
 	tcp_init_congestion_control(sk);
 	tcp_init_buffer_space(sk);
 }
diff --git a/net/ipv4/tcp_nv.c b/net/ipv4/tcp_nv.c
index 0b5a05b..ddbce73 100644
--- a/net/ipv4/tcp_nv.c
+++ b/net/ipv4/tcp_nv.c
@@ -146,7 +146,7 @@ static void tcpnv_init(struct sock *sk)
 	 * within a datacenter, where we have reasonable estimates of
 	 * RTTs
 	 */
-	base_rtt = tcp_call_bpf(sk, BPF_SOCK_OPS_BASE_RTT);
+	base_rtt = tcp_call_bpf(sk, BPF_SOCK_OPS_BASE_RTT, 0, NULL);
 	if (base_rtt > 0) {
 		ca->nv_base_rtt = base_rtt;
 		ca->nv_lower_bound_rtt = (base_rtt * 205) >> 8; /* 80% */
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 04be9f83..b093985 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3468,7 +3468,7 @@ int tcp_connect(struct sock *sk)
 	struct sk_buff *buff;
 	int err;
 
-	tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB);
+	tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL);
 
 	if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
 		return -EHOSTUNREACH; /* Routing failure or similar. */
-- 
2.9.5