On 06/15/2017 10:08 PM, Lawrence Brakmo wrote:
Added support for changing congestion control for SOCKET_OPS bps
programs through the setsockopt bpf helper function. It also adds
a new SOCKET_OPS op, BPF_SOCKET_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 <bra...@fb.com>
I like the use-case! ;)
---
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 | 15 ++++++++++-----
net/ipv4/tcp_input.c | 3 ++-
net/ipv4/tcp_output.c | 8 +++++---
7 files changed, 38 insertions(+), 13 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 29c27dc..371b1bd 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1001,7 +1001,9 @@ 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);
@@ -2039,4 +2041,9 @@ 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_SOCKET_OPS_NEEDS_ECN) == 1);
+}
#endif /* _TCP_H */
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c3490d3..8d1d2b7 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -776,6 +776,9 @@ enum {
* passive connection is
* established
*/
+ BPF_SOCKET_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 9ff567c..4325aba 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2716,8 +2716,15 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_socket_ops_kern *,
bpf_socket,
}
} else if (level == SOL_TCP &&
bpf_socket->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_socket->op > BPF_SOCKET_OPS_NEEDS_ECN)
+ /* replacing an existing ca */
+ tcp_reinit_congestion_control(sk,
+ inet_csk(sk)->icsk_ca_ops);
Can you elaborate on the sematics of BPF_SOCKET_OPS_NEEDS_ECN?
It's called from tcp_bpf_ca_needs_ecn(), so if someone sets a cong ctl
from that callback, or any other bpf_socket->op > BPF_SOCKET_OPS_NEEDS_ECN
then we call tcp_reinit_congestion_control()? Why 'bpf_socket->op > ..'?
Could the needs_ecn implementation detail be hidden altogether from the
BPF prog?
+ } else {
+ ret = -EINVAL;
+ }
} else {
ret = -EINVAL;
}
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index cc8fd8b..07984ea 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2478,7 +2478,7 @@ 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..e6f3717 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);
@@ -334,7 +334,7 @@ int tcp_set_allowed_congestion_control(char *val)
}
/* Change congestion control for socket */
-int tcp_set_congestion_control(struct sock *sk, const char *name)
+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;
@@ -344,7 +344,10 @@ int tcp_set_congestion_control(struct sock *sk, const char
*name)
return -EPERM;
rcu_read_lock();
- ca = __tcp_ca_find_autoload(name);
+ if (!load)
+ ca = tcp_ca_find(name);
+ else
+ ca = __tcp_ca_find_autoload(name);
From BPF program side, we call with !load since we're not allowed
to sleep under RCU, that's correct ...
/* No change asking for existing value */
if (ca == icsk->icsk_ca_ops) {
icsk->icsk_ca_setsockopt = 1;
@@ -352,8 +355,10 @@ int tcp_set_congestion_control(struct sock *sk, const char
*name)
}
if (!ca)
err = -ENOENT;
+ else if (!load)
+ icsk->icsk_ca_ops = ca;
... but don't we also need to hold a module ref in this case as done
below?
Meaning, tcp_ca_find() could return a ca that was previously loaded
to the tcp_cong_list as module, then resulting in ref count imbalance
when set from BPF?
else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) ||
- ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)))
+ ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)))
Nit: slipped in?
err = -EPERM;
else if (!try_module_get(ca->owner))
err = -EBUSY;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e0d688a..14c889f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6192,7 +6192,8 @@ static void tcp_ecn_create_request(struct request_sock
*req,
ecn_ok = net->ipv4.sysctl_tcp_ecn || ecn_ok_dst;
if ((!ect && ecn_ok) || tcp_ca_needs_ecn(listen_sk) ||
- (ecn_ok_dst & DST_FEATURE_ECN_CA))
+ (ecn_ok_dst & DST_FEATURE_ECN_CA) ||
+ tcp_bpf_ca_needs_ecn((struct sock *)req))
inet_rsk(req)->ecn_ok = 1;
}
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 9124d3d..30660ee 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -316,7 +316,8 @@ static void tcp_ecn_send_synack(struct sock *sk, struct
sk_buff *skb)
TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
if (!(tp->ecn_flags & TCP_ECN_OK))
TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
- else if (tcp_ca_needs_ecn(sk))
+ else if (tcp_ca_needs_ecn(sk) ||
+ tcp_bpf_ca_needs_ecn(sk))
INET_ECN_xmit(sk);
}
@@ -324,8 +325,9 @@ static void tcp_ecn_send_synack(struct sock *sk, struct
sk_buff *skb)
static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
{
struct tcp_sock *tp = tcp_sk(sk);
+ bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk);
bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 ||
- tcp_ca_needs_ecn(sk);
+ tcp_ca_needs_ecn(sk) || bpf_needs_ecn;
if (!use_ecn) {
const struct dst_entry *dst = __sk_dst_get(sk);
@@ -339,7 +341,7 @@ static void tcp_ecn_send_syn(struct sock *sk, struct
sk_buff *skb)
if (use_ecn) {
TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
tp->ecn_flags = TCP_ECN_OK;
- if (tcp_ca_needs_ecn(sk))
+ if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
INET_ECN_xmit(sk);
}
}
