bpf: Support passing args to sock_ops bpf function

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 <brakmo@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

6 files changed, 42 insertions, 10 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index daa5a676335f..20384c4bed25 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 6092eaff61cf..093e967a2960 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -2006,7 +2006,7 @@ 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;
@@ -2019,6 +2019,8 @@ 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(*args));
 
         ret = BPF_CGROUP_RUN_PROG_SOCK_OPS(&sock_ops);
         if (ret == 0)
@@ -2027,18 +2029,46 @@ static inline int tcp_call_bpf(struct sock *sk, int op)
                 ret = -1;
         return ret;
 }
+
+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);
+}
+
 #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_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;
+}
+
 #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;
@@ -2049,7 +2079,7 @@ 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;
@@ -2058,7 +2088,7 @@ 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 406c19d6016b..8d5874c2c4ff 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -952,8 +952,9 @@ 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 d7cf861bf699..88b62441e7e9 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 0b5a05bd82e3..ddbce73edae8 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 95461f02ac9a..d12f7f71c1c4 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3469,7 +3469,7 @@ 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. */