Re: [PATCH net-next v3 10/15] bpf: Add support for changing congestion control

[kbuild test robot]

Hi Lawrence,

[auto build test ERROR on net-next/master]

url:
https://github.com/0day-ci/linux/commits/Lawrence-Brakmo/bpf-BPF-support-for-sock_ops/20170620-142609
config: i386-randconfig-i0-201725 (attached as .config)
compiler: gcc-4.8 (Debian 4.8.4-1) 4.8.4
reproduce:
# save the attached .config to linux build tree
make ARCH=i386 

All errors (new ones prefixed by >>):

   net/built-in.o: In function `bpf_setsockopt':
>> (.text+0x326e9): undefined reference to `tcp_setsockopt'
   net/built-in.o: In function `bpf_setsockopt':
>> (.text+0x326f9): undefined reference to `tcp_set_congestion_control'
   net/built-in.o: In function `bpf_setsockopt':
>> (.text+0x32712): undefined reference to `tcp_reinit_congestion_control'

---
0-DAY kernel test infrastructureOpen Source Technology Center
https://lists.01.org/pipermail/kbuild-all   Intel Corporation


.config.gz
Description: application/gzip

[PATCH net-next v3 10/15] bpf: Add support for changing congestion control

[Lawrence Brakmo]

Added support for changing congestion control for SOCK_OPS bpf
programs through the setsockopt bpf helper function. It also adds
a new SOCK_OPS op, BPF_SOCK_OPS_NEEDS_ECN, that is needed for
congestion controls, like dctcp, that need to enable ECN in the
SYN packets.

Signed-off-by: Lawrence Brakmo 
---
 include/net/tcp.h|  9 -
 include/uapi/linux/bpf.h |  3 +++
 net/core/filter.c| 11 +--
 net/ipv4/tcp.c   |  2 +-
 net/ipv4/tcp_cong.c  | 32 ++--
 net/ipv4/tcp_input.c |  3 ++-
 net/ipv4/tcp_output.c|  8 +---
 7 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index ff806d7..58d67be 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1003,7 +1003,9 @@ void tcp_get_default_congestion_control(char *name);
 void tcp_get_available_congestion_control(char *buf, size_t len);
 void tcp_get_allowed_congestion_control(char *buf, size_t len);
 int tcp_set_allowed_congestion_control(char *allowed);
-int tcp_set_congestion_control(struct sock *sk, const char *name);
+int tcp_set_congestion_control(struct sock *sk, const char *name, bool load);
+void tcp_reinit_congestion_control(struct sock *sk,
+  const struct tcp_congestion_ops *ca);
 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
 
@@ -2072,4 +2074,9 @@ static inline u32 tcp_rwnd_init_bpf(struct sock *sk, bool 
is_req_sock)
rwnd = 0;
return rwnd;
 }
+
+static inline bool tcp_bpf_ca_needs_ecn(struct sock *sk)
+{
+   return (tcp_call_bpf(sk, true, BPF_SOCK_OPS_NEEDS_ECN) == 1);
+}
 #endif /* _TCP_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 4856d16..c222059 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -776,6 +776,9 @@ enum {
 * passive connection is
 * established
 */
+   BPF_SOCK_OPS_NEEDS_ECN, /* If connection's congestion control
+* needs ECN
+*/
 };
 
 #endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/net/core/filter.c b/net/core/filter.c
index b114ae1..bbf8f78 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2716,8 +2716,15 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, 
bpf_sock,
}
} else if (level == SOL_TCP &&
   sk->sk_prot->setsockopt == tcp_setsockopt) {
-   /* Place holder */
-   ret = -EINVAL;
+   if (optname == TCP_CONGESTION) {
+   ret = tcp_set_congestion_control(sk, optval, false);
+   if (!ret && bpf_sock->op > BPF_SOCK_OPS_NEEDS_ECN)
+   /* replacing an existing ca */
+   tcp_reinit_congestion_control(sk,
+   inet_csk(sk)->icsk_ca_ops);
+   } else {
+   ret = -EINVAL;
+   }
} else {
ret = -EINVAL;
}
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 058f509..9476fd6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2479,7 +2479,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level,
name[val] = 0;
 
lock_sock(sk);
-   err = tcp_set_congestion_control(sk, name);
+   err = tcp_set_congestion_control(sk, name, true);
release_sock(sk);
return err;
}
diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
index 324c9bc..fde983f 100644
--- a/net/ipv4/tcp_cong.c
+++ b/net/ipv4/tcp_cong.c
@@ -189,8 +189,8 @@ void tcp_init_congestion_control(struct sock *sk)
INET_ECN_dontxmit(sk);
 }
 
-static void tcp_reinit_congestion_control(struct sock *sk,
- const struct tcp_congestion_ops *ca)
+void tcp_reinit_congestion_control(struct sock *sk,
+  const struct tcp_congestion_ops *ca)
 {
struct inet_connection_sock *icsk = inet_csk(sk);
 
@@ -333,8 +333,12 @@ int tcp_set_allowed_congestion_control(char *val)
return ret;
 }
 
-/* Change congestion control for socket */
-int tcp_set_congestion_control(struct sock *sk, const char *name)
+/* Change congestion control for socket. If load is false, then it is the
+ * responsibility of the caller to call tcp_init_congestion_control or
+ * tcp_reinit_congestion_control (if the current congestion control was
+ * already initialized.
+ */
+int tcp_set_congestion_control(struct sock *sk, const char *name, bool load)
 {
struct inet_connection_sock *icsk = inet_csk(sk);
const struct tcp_congestion_ops *ca;
@@ -344,21 +348,29 @@ int