tcp/udp: Make early_demux back namespacified.

Commit e21145a9871a ("ipv4: namespacify ip_early_demux sysctl knob") made
it possible to enable/disable early_demux on a per-netns basis.  Then, we
introduced two knobs, tcp_early_demux and udp_early_demux, to switch it for
TCP/UDP in commit dddb64bcb346 ("net: Add sysctl to toggle early demux for
tcp and udp").  However, the .proc_handler() was wrong and actually
disabled us from changing the behaviour in each netns.

We can execute early_demux if net.ipv4.ip_early_demux is on and each proto
.early_demux() handler is not NULL.  When we toggle (tcp|udp)_early_demux,
the change itself is saved in each netns variable, but the .early_demux()
handler is a global variable, so the handler is switched based on the
init_net's sysctl variable.  Thus, netns (tcp|udp)_early_demux knobs have
nothing to do with the logic.  Whether we CAN execute proto .early_demux()
is always decided by init_net's sysctl knob, and whether we DO it or not is
by each netns ip_early_demux knob.

This patch namespacifies (tcp|udp)_early_demux again.  For now, the users
of the .early_demux() handler are TCP and UDP only, and they are called
directly to avoid retpoline.  So, we can remove the .early_demux() handler
from inet6?_protos and need not dereference them in ip6?_rcv_finish_core().
If another proto needs .early_demux(), we can restore it at that time.

Fixes: dddb64bcb346 ("net: Add sysctl to toggle early demux for tcp and udp")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20220713175207.7727-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 2 insertions, 57 deletions

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 108fd86f2718..130e9c130311 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -350,61 +350,6 @@ bad_key:
 	return ret;
 }
 
-static void proc_configure_early_demux(int enabled, int protocol)
-{
-	struct net_protocol *ipprot;
-#if IS_ENABLED(CONFIG_IPV6)
-	struct inet6_protocol *ip6prot;
-#endif
-
-	rcu_read_lock();
-
-	ipprot = rcu_dereference(inet_protos[protocol]);
-	if (ipprot)
-		ipprot->early_demux = enabled ? ipprot->early_demux_handler :
-						NULL;
-
-#if IS_ENABLED(CONFIG_IPV6)
-	ip6prot = rcu_dereference(inet6_protos[protocol]);
-	if (ip6prot)
-		ip6prot->early_demux = enabled ? ip6prot->early_demux_handler :
-						 NULL;
-#endif
-	rcu_read_unlock();
-}
-
-static int proc_tcp_early_demux(struct ctl_table *table, int write,
-				void *buffer, size_t *lenp, loff_t *ppos)
-{
-	int ret = 0;
-
-	ret = proc_dou8vec_minmax(table, write, buffer, lenp, ppos);
-
-	if (write && !ret) {
-		int enabled = init_net.ipv4.sysctl_tcp_early_demux;
-
-		proc_configure_early_demux(enabled, IPPROTO_TCP);
-	}
-
-	return ret;
-}
-
-static int proc_udp_early_demux(struct ctl_table *table, int write,
-				void *buffer, size_t *lenp, loff_t *ppos)
-{
-	int ret = 0;
-
-	ret = proc_dou8vec_minmax(table, write, buffer, lenp, ppos);
-
-	if (write && !ret) {
-		int enabled = init_net.ipv4.sysctl_udp_early_demux;
-
-		proc_configure_early_demux(enabled, IPPROTO_UDP);
-	}
-
-	return ret;
-}
-
 static int proc_tfo_blackhole_detect_timeout(struct ctl_table *table,
 					     int write, void *buffer,
 					     size_t *lenp, loff_t *ppos)
@@ -707,14 +652,14 @@ static struct ctl_table ipv4_net_table[] = {
 		.data           = &init_net.ipv4.sysctl_udp_early_demux,
 		.maxlen         = sizeof(u8),
 		.mode           = 0644,
-		.proc_handler   = proc_udp_early_demux
+		.proc_handler   = proc_dou8vec_minmax,
 	},
 	{
 		.procname       = "tcp_early_demux",
 		.data           = &init_net.ipv4.sysctl_tcp_early_demux,
 		.maxlen         = sizeof(u8),
 		.mode           = 0644,
-		.proc_handler   = proc_tcp_early_demux
+		.proc_handler   = proc_dou8vec_minmax,
 	},
 	{
 		.procname       = "nexthop_compat_mode",