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tcp/udp: Make early_demux back namespacified.
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Commit e21145a ("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 dddb64b ("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: dddb64b ("net: Add sysctl to toggle early demux for tcp and udp")
Signed-off-by: Kuniyuki Iwashima <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
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@q2ven @kuba-moo
q2ven authored and kuba-moo committed Jul 16, 2022
1 parent df254d4 commit 1105258
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Showing 9 changed files with 45 additions and 114 deletions.
4 changes: 0 additions & 4 deletions include/net/protocol.h
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Original file line number Diff line number Diff line change
Expand Up @@ -35,8 +35,6 @@

/* This is used to register protocols. */
struct net_protocol {
int (*early_demux)(struct sk_buff *skb);
int (*early_demux_handler)(struct sk_buff *skb);
int (*handler)(struct sk_buff *skb);

/* This returns an error if we weren't able to handle the error. */
Expand All @@ -52,8 +50,6 @@ struct net_protocol {

#if IS_ENABLED(CONFIG_IPV6)
struct inet6_protocol {
void (*early_demux)(struct sk_buff *skb);
void (*early_demux_handler)(struct sk_buff *skb);
int (*handler)(struct sk_buff *skb);

/* This returns an error if we weren't able to handle the error. */
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2 changes: 1 addition & 1 deletion include/net/tcp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -932,7 +932,7 @@ extern const struct inet_connection_sock_af_ops ipv6_specific;

INDIRECT_CALLABLE_DECLARE(void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb));
INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *skb));
INDIRECT_CALLABLE_DECLARE(void tcp_v6_early_demux(struct sk_buff *skb));
void tcp_v6_early_demux(struct sk_buff *skb);

#endif

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2 changes: 1 addition & 1 deletion include/net/udp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -167,7 +167,7 @@ static inline void udp_csum_pull_header(struct sk_buff *skb)
typedef struct sock *(*udp_lookup_t)(const struct sk_buff *skb, __be16 sport,
__be16 dport);

INDIRECT_CALLABLE_DECLARE(void udp_v6_early_demux(struct sk_buff *));
void udp_v6_early_demux(struct sk_buff *skb);
INDIRECT_CALLABLE_DECLARE(int udpv6_rcv(struct sk_buff *));

struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
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14 changes: 2 additions & 12 deletions net/ipv4/af_inet.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1710,24 +1710,14 @@ static const struct net_protocol igmp_protocol = {
};
#endif

/* thinking of making this const? Don't.
* early_demux can change based on sysctl.
*/
static struct net_protocol tcp_protocol = {
.early_demux = tcp_v4_early_demux,
.early_demux_handler = tcp_v4_early_demux,
static const struct net_protocol tcp_protocol = {
.handler = tcp_v4_rcv,
.err_handler = tcp_v4_err,
.no_policy = 1,
.icmp_strict_tag_validation = 1,
};

/* thinking of making this const? Don't.
* early_demux can change based on sysctl.
*/
static struct net_protocol udp_protocol = {
.early_demux = udp_v4_early_demux,
.early_demux_handler = udp_v4_early_demux,
static const struct net_protocol udp_protocol = {
.handler = udp_rcv,
.err_handler = udp_err,
.no_policy = 1,
Expand Down
37 changes: 22 additions & 15 deletions net/ipv4/ip_input.c
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Original file line number Diff line number Diff line change
Expand Up @@ -312,14 +312,13 @@ static bool ip_can_use_hint(const struct sk_buff *skb, const struct iphdr *iph,
ip_hdr(hint)->tos == iph->tos;
}

INDIRECT_CALLABLE_DECLARE(int udp_v4_early_demux(struct sk_buff *));
INDIRECT_CALLABLE_DECLARE(int tcp_v4_early_demux(struct sk_buff *));
int tcp_v4_early_demux(struct sk_buff *skb);
int udp_v4_early_demux(struct sk_buff *skb);
static int ip_rcv_finish_core(struct net *net, struct sock *sk,
struct sk_buff *skb, struct net_device *dev,
const struct sk_buff *hint)
{
const struct iphdr *iph = ip_hdr(skb);
int (*edemux)(struct sk_buff *skb);
int err, drop_reason;
struct rtable *rt;

Expand All @@ -332,21 +331,29 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
goto drop_error;
}

if (net->ipv4.sysctl_ip_early_demux &&
if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
!skb_dst(skb) &&
!skb->sk &&
!ip_is_fragment(iph)) {
const struct net_protocol *ipprot;
int protocol = iph->protocol;

ipprot = rcu_dereference(inet_protos[protocol]);
if (ipprot && (edemux = READ_ONCE(ipprot->early_demux))) {
err = INDIRECT_CALL_2(edemux, tcp_v4_early_demux,
udp_v4_early_demux, skb);
if (unlikely(err))
goto drop_error;
/* must reload iph, skb->head might have changed */
iph = ip_hdr(skb);
switch (iph->protocol) {
case IPPROTO_TCP:
if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux)) {
tcp_v4_early_demux(skb);

/* must reload iph, skb->head might have changed */
iph = ip_hdr(skb);
}
break;
case IPPROTO_UDP:
if (READ_ONCE(net->ipv4.sysctl_udp_early_demux)) {
err = udp_v4_early_demux(skb);
if (unlikely(err))
goto drop_error;

/* must reload iph, skb->head might have changed */
iph = ip_hdr(skb);
}
break;
}
}

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59 changes: 2 additions & 57 deletions net/ipv4/sysctl_net_ipv4.c
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Original file line number Diff line number Diff line change
Expand Up @@ -350,61 +350,6 @@ static int proc_tcp_fastopen_key(struct ctl_table *table, int write,
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)
Expand Down Expand Up @@ -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",
Expand Down
23 changes: 13 additions & 10 deletions net/ipv6/ip6_input.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,20 +45,23 @@
#include <net/inet_ecn.h>
#include <net/dst_metadata.h>

INDIRECT_CALLABLE_DECLARE(void tcp_v6_early_demux(struct sk_buff *));
static void ip6_rcv_finish_core(struct net *net, struct sock *sk,
struct sk_buff *skb)
{
void (*edemux)(struct sk_buff *skb);

if (net->ipv4.sysctl_ip_early_demux && !skb_dst(skb) && skb->sk == NULL) {
const struct inet6_protocol *ipprot;

ipprot = rcu_dereference(inet6_protos[ipv6_hdr(skb)->nexthdr]);
if (ipprot && (edemux = READ_ONCE(ipprot->early_demux)))
INDIRECT_CALL_2(edemux, tcp_v6_early_demux,
udp_v6_early_demux, skb);
if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
!skb_dst(skb) && !skb->sk) {
switch (ipv6_hdr(skb)->nexthdr) {
case IPPROTO_TCP:
if (READ_ONCE(net->ipv4.sysctl_tcp_early_demux))
tcp_v6_early_demux(skb);
break;
case IPPROTO_UDP:
if (READ_ONCE(net->ipv4.sysctl_udp_early_demux))
udp_v6_early_demux(skb);
break;
}
}

if (!skb_valid_dst(skb))
ip6_route_input(skb);
}
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9 changes: 2 additions & 7 deletions net/ipv6/tcp_ipv6.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1822,7 +1822,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
goto discard_it;
}

INDIRECT_CALLABLE_SCOPE void tcp_v6_early_demux(struct sk_buff *skb)
void tcp_v6_early_demux(struct sk_buff *skb)
{
const struct ipv6hdr *hdr;
const struct tcphdr *th;
Expand Down Expand Up @@ -2176,12 +2176,7 @@ struct proto tcpv6_prot = {
};
EXPORT_SYMBOL_GPL(tcpv6_prot);

/* thinking of making this const? Don't.
* early_demux can change based on sysctl.
*/
static struct inet6_protocol tcpv6_protocol = {
.early_demux = tcp_v6_early_demux,
.early_demux_handler = tcp_v6_early_demux,
static const struct inet6_protocol tcpv6_protocol = {
.handler = tcp_v6_rcv,
.err_handler = tcp_v6_err,
.flags = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
Expand Down
9 changes: 2 additions & 7 deletions net/ipv6/udp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1052,7 +1052,7 @@ static struct sock *__udp6_lib_demux_lookup(struct net *net,
return NULL;
}

INDIRECT_CALLABLE_SCOPE void udp_v6_early_demux(struct sk_buff *skb)
void udp_v6_early_demux(struct sk_buff *skb)
{
struct net *net = dev_net(skb->dev);
const struct udphdr *uh;
Expand Down Expand Up @@ -1660,12 +1660,7 @@ int udpv6_getsockopt(struct sock *sk, int level, int optname,
return ipv6_getsockopt(sk, level, optname, optval, optlen);
}

/* thinking of making this const? Don't.
* early_demux can change based on sysctl.
*/
static struct inet6_protocol udpv6_protocol = {
.early_demux = udp_v6_early_demux,
.early_demux_handler = udp_v6_early_demux,
static const struct inet6_protocol udpv6_protocol = {
.handler = udpv6_rcv,
.err_handler = udpv6_err,
.flags = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
Expand Down

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