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Merge branch 'hash-rethink' 

Akhmat Karakotov says:

====================
Make hash rethink configurable

As it was shown in the report by Alexander Azimov, hash rethink at the
client-side may lead to connection timeout toward stateful anycast
services. Tom Herbert created a patchset to address this issue by applying
hash rethink only after a negative routing event (3RTOs) [1]. This change
also affects server-side behavior, which we found undesirable. This
patchset changes defaults in a way to make them safe: hash rethink at the
client-side is disabled and enabled at the server-side upon each RTO
event or in case of duplicate acknowledgments.

This patchset provides two options to change default behaviour. The hash
rethink may be disabled at the server-side by the new sysctl option.
Changes in the sysctl option don't affect default behavior at the
client-side.

Hash rethink can also be enabled/disabled with socket option or bpf
syscalls which ovewrite both default and sysctl settings. This socket
option is available on both client and server-side. This should provide
mechanics to enable hash rethink inside administrative domain, such as DC,
where hash rethink at the client-side can be desirable.

[1] https://lore.kernel.org/netdev/20210809185314.38187-1-tom@herbertland.com/

v2:
	- Changed sysctl default to ENABLED in all patches. Reduced sysctl
	  and socket option size to u8. Fixed netns bug reported by kernel
	  test robot.

v3:
	- Fixed bug with bad u8 comparison. Moved sk_txrehash to use less
	  bytes in struct. Added WRITE_ONCE() in setsockopt in and
	  READ_ONCE() in tcp_rtx_synack.

v4:
	- Rebase and add documentation for sysctl option.

v5:
	- Move sk_txrehash out of busy poll ifdef.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2022-01-31 15:05:25 +00:00
parent 678dfd5280 cb6cd2cec7
commit 01b2a99515
15 changed files with 83 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
Documentation/admin-guide/sysctl/net.rst
View File

@ -365,6 +365,15 @@ new netns has been created.
Default : 0 (for compatibility reasons)
txrehash
--------
Controls default hash rethink behaviour on listening socket when SO_TXREHASH
option is set to SOCK_TXREHASH_DEFAULT (i. e. not overridden by setsockopt).
If set to 1 (default), hash rethink is performed on listening socket.
If set to 0, hash rethink is not performed.
2. /proc/sys/net/unix - Parameters for Unix domain sockets
----------------------------------------------------------

2
arch/alpha/include/uapi/asm/socket.h
View File

@ -133,6 +133,8 @@
#define SO_RESERVE_MEM 73
#define SO_TXREHASH 74
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/mips/include/uapi/asm/socket.h
View File

@ -144,6 +144,8 @@
#define SO_RESERVE_MEM 73
#define SO_TXREHASH 74
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/parisc/include/uapi/asm/socket.h
View File

@ -125,6 +125,8 @@
#define SO_RESERVE_MEM 0x4047
#define SO_TXREHASH 0x4048
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64

2
arch/sparc/include/uapi/asm/socket.h
View File

@ -126,6 +126,8 @@
#define SO_RESERVE_MEM 0x0052
#define SO_TXREHASH 0x0053
#if !defined(__KERNEL__)

1
include/net/netns/core.h
View File

@ -10,6 +10,7 @@ struct netns_core {
struct ctl_table_header *sysctl_hdr;
int sysctl_somaxconn;
u8 sysctl_txrehash;
#ifdef CONFIG_PROC_FS
struct prot_inuse __percpu *prot_inuse;

28
include/net/sock.h
View File

@ -316,6 +316,7 @@ struct sk_filter;
* @sk_rcvtimeo: %SO_RCVTIMEO setting
* @sk_sndtimeo: %SO_SNDTIMEO setting
* @sk_txhash: computed flow hash for use on transmit
* @sk_txrehash: enable TX hash rethink
* @sk_filter: socket filtering instructions
* @sk_timer: sock cleanup timer
* @sk_stamp: time stamp of last packet received
@ -491,6 +492,7 @@ struct sock {
u32 sk_ack_backlog;
u32 sk_max_ack_backlog;
kuid_t sk_uid;
u8 sk_txrehash;
#ifdef CONFIG_NET_RX_BUSY_POLL
u8 sk_prefer_busy_poll;
u16 sk_busy_poll_budget;
@ -587,6 +589,18 @@ static inline bool sk_user_data_is_nocopy(const struct sock *sk)
__tmp | SK_USER_DATA_NOCOPY); \
})
static inline
struct net *sock_net(const struct sock *sk)
{
return read_pnet(&sk->sk_net);
}
static inline
void sock_net_set(struct sock *sk, struct net *net)
{
write_pnet(&sk->sk_net, net);
}
/*
* SK_CAN_REUSE and SK_NO_REUSE on a socket mean that the socket is OK
* or not whether his port will be reused by someone else. SK_FORCE_REUSE
@ -2054,7 +2068,7 @@ static inline void sk_set_txhash(struct sock *sk)
static inline bool sk_rethink_txhash(struct sock *sk)
{
if (sk->sk_txhash) {
if (sk->sk_txhash && sk->sk_txrehash == SOCK_TXREHASH_ENABLED) {
sk_set_txhash(sk);
return true;
}
@ -2704,18 +2718,6 @@ static inline void sk_eat_skb(struct sock *sk, struct sk_buff *skb)
__kfree_skb(skb);
}
static inline
struct net *sock_net(const struct sock *sk)
{
return read_pnet(&sk->sk_net);
}
static inline
void sock_net_set(struct sock *sk, struct net *net)
{
write_pnet(&sk->sk_net, net);
}
static inline bool
skb_sk_is_prefetched(struct sk_buff *skb)
{

2
include/uapi/asm-generic/socket.h
View File

@ -128,6 +128,8 @@
#define SO_RESERVE_MEM 73
#define SO_TXREHASH 74
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))

4
include/uapi/linux/socket.h
View File

@ -31,4 +31,8 @@ struct __kernel_sockaddr_storage {
#define SOCK_BUF_LOCK_MASK (SOCK_SNDBUF_LOCK | SOCK_RCVBUF_LOCK)
#define SOCK_TXREHASH_DEFAULT ((u8)-1)
#define SOCK_TXREHASH_DISABLED 0
#define SOCK_TXREHASH_ENABLED 1
#endif /* _UAPI_LINUX_SOCKET_H */

10
net/core/filter.c
View File

@ -5091,6 +5091,13 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
case SO_REUSEPORT:
sk->sk_reuseport = valbool;
break;
case SO_TXREHASH:
if (val < -1 || val > 1) {
ret = -EINVAL;
break;
}
sk->sk_txrehash = (u8)val;
break;
default:
ret = -EINVAL;
}
@ -5269,6 +5276,9 @@ static int _bpf_getsockopt(struct sock *sk, int level, int optname,
case SO_REUSEPORT:
*((int *)optval) = sk->sk_reuseport;
break;
case SO_TXREHASH:
*((int *)optval) = sk->sk_txrehash;
break;
default:
goto err_clear;
}

2
net/core/net_namespace.c
View File

@ -364,6 +364,8 @@ out_undo:
static int __net_init net_defaults_init_net(struct net *net)
{
net->core.sysctl_somaxconn = SOMAXCONN;
net->core.sysctl_txrehash = SOCK_TXREHASH_ENABLED;
return 0;
}

14
net/core/sock.c
View File

@ -1447,6 +1447,15 @@ set_sndbuf:
break;
}
case SO_TXREHASH:
if (val < -1 || val > 1) {
ret = -EINVAL;
break;
}
/* Paired with READ_ONCE() in tcp_rtx_synack() */
WRITE_ONCE(sk->sk_txrehash, (u8)val);
break;
default:
ret = -ENOPROTOOPT;
break;
@ -1834,6 +1843,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
v.val = sk->sk_reserved_mem;
break;
case SO_TXREHASH:
v.val = sk->sk_txrehash;
break;
default:
/* We implement the SO_SNDLOWAT etc to not be settable
* (1003.1g 7).
@ -3279,6 +3292,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
sk->sk_pacing_rate = ~0UL;
WRITE_ONCE(sk->sk_pacing_shift, 10);
sk->sk_incoming_cpu = -1;
sk->sk_txrehash = SOCK_TXREHASH_DEFAULT;
sk_rx_queue_clear(sk);
/*

14
net/core/sysctl_net_core.c
View File

@ -593,6 +593,15 @@ static struct ctl_table netns_core_table[] = {
.extra1 = SYSCTL_ZERO,
.proc_handler = proc_dointvec_minmax
},
{
.procname = "txrehash",
.data = &init_net.core.sysctl_txrehash,
.maxlen = sizeof(u8),
.mode = 0644,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
.proc_handler = proc_dou8vec_minmax,
},
{ }
};
@ -611,7 +620,7 @@ __setup("fb_tunnels=", fb_tunnels_only_for_init_net_sysctl_setup);
static __net_init int sysctl_core_net_init(struct net *net)
{
struct ctl_table *tbl;
struct ctl_table *tbl, *tmp;
tbl = netns_core_table;
if (!net_eq(net, &init_net)) {
@ -619,7 +628,8 @@ static __net_init int sysctl_core_net_init(struct net *net)
if (tbl == NULL)
goto err_dup;
tbl[0].data = &net->core.sysctl_somaxconn;
for (tmp = tbl; tmp->procname; tmp++)
tmp->data += (char *)net - (char *)&init_net;
/* Don't export any sysctls to unprivileged users */
if (net->user_ns != &init_user_ns) {

3
net/ipv4/inet_connection_sock.c
View File

@ -1046,6 +1046,9 @@ int inet_csk_listen_start(struct sock *sk)
sk->sk_ack_backlog = 0;
inet_csk_delack_init(sk);
if (sk->sk_txrehash == SOCK_TXREHASH_DEFAULT)
sk->sk_txrehash = READ_ONCE(sock_net(sk)->core.sysctl_txrehash);
/* There is race window here: we announce ourselves listening,
* but this transition is still not validated by get_port().
* It is OK, because this socket enters to hash table only

4
net/ipv4/tcp_output.c
View File

@ -4092,7 +4092,9 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
struct flowi fl;
int res;
tcp_rsk(req)->txhash = net_tx_rndhash();
/* Paired with WRITE_ONCE() in sock_setsockopt() */
if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED)
tcp_rsk(req)->txhash = net_tx_rndhash();
res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL,
NULL);
if (!res) {