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Merge branch 'improve-bpf-tcp-cc-init'

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Neal Cardwell says:

====================
This patch series reorganizes TCP congestion control initialization so that if
EBPF code called by tcp_init_transfer() sets the congestion control algorithm
by calling setsockopt(TCP_CONGESTION) then the TCP stack initializes the
congestion control module immediately, instead of having tcp_init_transfer()
later initialize the congestion control module.

This increases flexibility for the EBPF code that runs at connection
establishment time, and simplifies the code.

This has the following benefits:

(1) This allows CC module customizations made by the EBPF called in
    tcp_init_transfer() to persist, and not be wiped out by a later
    call to tcp_init_congestion_control() in tcp_init_transfer().

(2) Does not flip the order of EBPF and CC init, to avoid causing bugs
    for existing code upstream that depends on the current order.

(3) Does not cause 2 initializations for for CC in the case where the
    EBPF called in tcp_init_transfer() wants to set the CC to a new CC
    algorithm.

(4) Allows follow-on simplifications to the code in net/core/filter.c
    and net/ipv4/tcp_cong.c, which currently both have some complexity
    to special-case CC initialization to avoid double CC
    initialization if EBPF sets the CC.

changes in v2:

o rebase onto bpf-next

o add another follow-on simplification suggested by Martin KaFai Lau:
   "tcp: simplify tcp_set_congestion_control() load=false case"

changes in v3:

o no change in commits

o resent patch series from @gmail.com, since mail from ncardwell@google.com
  stopped being accepted at netdev@vger.kernel.org mid-way through processing
  the v2 patch series (between patches 2 and 3), confusing patchwork about
  which patches belonged to the v2 patch series
====================

Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alexei Starovoitov 2020-09-10 20:53:01 -07:00
commit 2bab48c5be
6 changed files with 19 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
include/net/inet_connection_sock.h
View File

@ -96,7 +96,8 @@ struct inet_connection_sock {
void (*icsk_clean_acked)(struct sock *sk, u32 acked_seq);
struct hlist_node icsk_listen_portaddr_node;
unsigned int (*icsk_sync_mss)(struct sock *sk, u32 pmtu);
__u8 icsk_ca_state:6,
__u8 icsk_ca_state:5,
icsk_ca_initialized:1,
icsk_ca_setsockopt:1,
icsk_ca_dst_locked:1;
__u8 icsk_retransmits;

2
include/net/tcp.h
View File

@ -1104,7 +1104,7 @@ 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, bool load,
bool reinit, bool cap_net_admin);
bool cap_net_admin);
u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);

18
net/core/filter.c
View File

@ -4313,10 +4313,8 @@ static const struct bpf_func_proto bpf_get_socket_uid_proto = {
.arg1_type = ARG_PTR_TO_CTX,
};
#define SOCKOPT_CC_REINIT (1 << 0)
static int _bpf_setsockopt(struct sock *sk, int level, int optname,
char *optval, int optlen, u32 flags)
char *optval, int optlen)
{
char devname[IFNAMSIZ];
int val, valbool;
@ -4449,13 +4447,11 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
sk->sk_prot->setsockopt == tcp_setsockopt) {
if (optname == TCP_CONGESTION) {
char name[TCP_CA_NAME_MAX];
bool reinit = flags & SOCKOPT_CC_REINIT;
strncpy(name, optval, min_t(long, optlen,
TCP_CA_NAME_MAX-1));
name[TCP_CA_NAME_MAX-1] = 0;
ret = tcp_set_congestion_control(sk, name, false,
reinit, true);
ret = tcp_set_congestion_control(sk, name, false, true);
} else {
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
@ -4615,9 +4611,7 @@ err_clear:
BPF_CALL_5(bpf_sock_addr_setsockopt, struct bpf_sock_addr_kern *, ctx,
int, level, int, optname, char *, optval, int, optlen)
{
u32 flags = 0;
return _bpf_setsockopt(ctx->sk, level, optname, optval, optlen,
flags);
return _bpf_setsockopt(ctx->sk, level, optname, optval, optlen);
}
static const struct bpf_func_proto bpf_sock_addr_setsockopt_proto = {
@ -4651,11 +4645,7 @@ static const struct bpf_func_proto bpf_sock_addr_getsockopt_proto = {
BPF_CALL_5(bpf_sock_ops_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
int, level, int, optname, char *, optval, int, optlen)
{
u32 flags = 0;
if (bpf_sock->op > BPF_SOCK_OPS_NEEDS_ECN)
flags |= SOCKOPT_CC_REINIT;
return _bpf_setsockopt(bpf_sock->sk, level, optname, optval, optlen,
flags);
return _bpf_setsockopt(bpf_sock->sk, level, optname, optval, optlen);
}
static const struct bpf_func_proto bpf_sock_ops_setsockopt_proto = {

3
net/ipv4/tcp.c
View File

@ -2698,6 +2698,7 @@ int tcp_disconnect(struct sock *sk, int flags)
if (icsk->icsk_ca_ops->release)
icsk->icsk_ca_ops->release(sk);
memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
icsk->icsk_ca_initialized = 0;
tcp_set_ca_state(sk, TCP_CA_Open);
tp->is_sack_reneg = 0;
tcp_clear_retrans(tp);
@ -3049,7 +3050,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level, int optname,
name[val] = 0;
lock_sock(sk);
err = tcp_set_congestion_control(sk, name, true, true,
err = tcp_set_congestion_control(sk, name, true,
ns_capable(sock_net(sk)->user_ns,
CAP_NET_ADMIN));
release_sock(sk);

27
net/ipv4/tcp_cong.c
View File

@ -176,7 +176,7 @@ void tcp_assign_congestion_control(struct sock *sk)
void tcp_init_congestion_control(struct sock *sk)
{
const struct inet_connection_sock *icsk = inet_csk(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
tcp_sk(sk)->prior_ssthresh = 0;
if (icsk->icsk_ca_ops->init)
@ -185,6 +185,7 @@ void tcp_init_congestion_control(struct sock *sk)
INET_ECN_xmit(sk);
else
INET_ECN_dontxmit(sk);
icsk->icsk_ca_initialized = 1;
}
static void tcp_reinit_congestion_control(struct sock *sk,
@ -340,7 +341,7 @@ out:
* already initialized.
*/
int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
bool reinit, bool cap_net_admin)
bool cap_net_admin)
{
struct inet_connection_sock *icsk = inet_csk(sk);
const struct tcp_congestion_ops *ca;
@ -361,28 +362,14 @@ int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
goto out;
}
if (!ca) {
if (!ca)
err = -ENOENT;
} else if (!load) {
const struct tcp_congestion_ops *old_ca = icsk->icsk_ca_ops;
if (bpf_try_module_get(ca, ca->owner)) {
if (reinit) {
tcp_reinit_congestion_control(sk, ca);
} else {
icsk->icsk_ca_ops = ca;
bpf_module_put(old_ca, old_ca->owner);
}
} else {
err = -EBUSY;
}
} else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin)) {
else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin))
err = -EPERM;
} else if (!bpf_try_module_get(ca, ca->owner)) {
else if (!bpf_try_module_get(ca, ca->owner))
err = -EBUSY;
} else {
else
tcp_reinit_congestion_control(sk, ca);
}
out:
rcu_read_unlock();
return err;

4
net/ipv4/tcp_input.c
View File

@ -5894,8 +5894,10 @@ void tcp_init_transfer(struct sock *sk, int bpf_op, struct sk_buff *skb)
tp->snd_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk));
tp->snd_cwnd_stamp = tcp_jiffies32;
icsk->icsk_ca_initialized = 0;
bpf_skops_established(sk, bpf_op, skb);
tcp_init_congestion_control(sk);
if (!icsk->icsk_ca_initialized)
tcp_init_congestion_control(sk);
tcp_init_buffer_space(sk);
}