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inet: implement lockless IP_MTU_DISCOVER

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inet->pmtudisc can be read locklessly.

Implement proper lockless reads and writes to inet->pmtudisc

ip_sock_set_mtu_discover() can now be called from arbitrary
contexts.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2023-09-22 03:42:15 +00:00 committed by David S. Miller
parent c9746e6a19
commit ceaa714138
7 changed files with 22 additions and 23 deletions
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13
include/net/ip.h
View File

@ -434,19 +434,22 @@ int ip_dont_fragment(const struct sock *sk, const struct dst_entry *dst)
static inline bool ip_sk_accept_pmtu(const struct sock *sk)
{
return inet_sk(sk)->pmtudisc != IP_PMTUDISC_INTERFACE &&
inet_sk(sk)->pmtudisc != IP_PMTUDISC_OMIT;
u8 pmtudisc = READ_ONCE(inet_sk(sk)->pmtudisc);
return pmtudisc != IP_PMTUDISC_INTERFACE &&
pmtudisc != IP_PMTUDISC_OMIT;
}
static inline bool ip_sk_use_pmtu(const struct sock *sk)
{
return inet_sk(sk)->pmtudisc < IP_PMTUDISC_PROBE;
return READ_ONCE(inet_sk(sk)->pmtudisc) < IP_PMTUDISC_PROBE;
}
static inline bool ip_sk_ignore_df(const struct sock *sk)
{
return inet_sk(sk)->pmtudisc < IP_PMTUDISC_DO ||
inet_sk(sk)->pmtudisc == IP_PMTUDISC_OMIT;
u8 pmtudisc = READ_ONCE(inet_sk(sk)->pmtudisc);
return pmtudisc < IP_PMTUDISC_DO || pmtudisc == IP_PMTUDISC_OMIT;
}
static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,

7
net/ipv4/ip_output.c
View File

@ -1387,8 +1387,8 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
struct ip_options *opt = NULL;
struct rtable *rt = (struct rtable *)cork->dst;
struct iphdr *iph;
u8 pmtudisc, ttl;
__be16 df = 0;
__u8 ttl;
skb = __skb_dequeue(queue);
if (!skb)
@ -1418,8 +1418,9 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
/* DF bit is set when we want to see DF on outgoing frames.
* If ignore_df is set too, we still allow to fragment this frame
* locally. */
if (inet->pmtudisc == IP_PMTUDISC_DO ||
inet->pmtudisc == IP_PMTUDISC_PROBE ||
pmtudisc = READ_ONCE(inet->pmtudisc);
if (pmtudisc == IP_PMTUDISC_DO ||
pmtudisc == IP_PMTUDISC_PROBE ||
(skb->len <= dst_mtu(&rt->dst) &&
ip_dont_fragment(sk, &rt->dst)))
df = htons(IP_DF);

17
net/ipv4/ip_sockglue.c
View File

@ -622,9 +622,7 @@ int ip_sock_set_mtu_discover(struct sock *sk, int val)
{
if (val < IP_PMTUDISC_DONT || val > IP_PMTUDISC_OMIT)
return -EINVAL;
lock_sock(sk);
inet_sk(sk)->pmtudisc = val;
release_sock(sk);
WRITE_ONCE(inet_sk(sk)->pmtudisc, val);
return 0;
}
EXPORT_SYMBOL(ip_sock_set_mtu_discover);
@ -1050,6 +1048,8 @@ int do_ip_setsockopt(struct sock *sk, int level, int optname,
return -EINVAL;
WRITE_ONCE(inet->mc_ttl, val);
return 0;
case IP_MTU_DISCOVER:
return ip_sock_set_mtu_discover(sk, val);
}
err = 0;
@ -1107,11 +1107,6 @@ int do_ip_setsockopt(struct sock *sk, int level, int optname,
case IP_TOS: /* This sets both TOS and Precedence */
__ip_sock_set_tos(sk, val);
break;
case IP_MTU_DISCOVER:
if (val < IP_PMTUDISC_DONT || val > IP_PMTUDISC_OMIT)
goto e_inval;
inet->pmtudisc = val;
break;
case IP_UNICAST_IF:
{
struct net_device *dev = NULL;
@ -1595,6 +1590,9 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname,
case IP_MULTICAST_TTL:
val = READ_ONCE(inet->mc_ttl);
goto copyval;
case IP_MTU_DISCOVER:
val = READ_ONCE(inet->pmtudisc);
goto copyval;
}
if (needs_rtnl)
@ -1634,9 +1632,6 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname,
case IP_TOS:
val = inet->tos;
break;
case IP_MTU_DISCOVER:
val = inet->pmtudisc;
break;
case IP_MTU:
{
struct dst_entry *dst;

2
net/ipv4/ping.c
View File

@ -551,7 +551,7 @@ void ping_err(struct sk_buff *skb, int offset, u32 info)
case ICMP_DEST_UNREACH:
if (code == ICMP_FRAG_NEEDED) { /* Path MTU discovery */
ipv4_sk_update_pmtu(skb, sk, info);
if (inet_sock->pmtudisc != IP_PMTUDISC_DONT) {
if (READ_ONCE(inet_sock->pmtudisc) != IP_PMTUDISC_DONT) {
err = EMSGSIZE;
harderr = 1;
break;

2
net/ipv4/raw.c
View File

@ -239,7 +239,7 @@ static void raw_err(struct sock *sk, struct sk_buff *skb, u32 info)
if (code > NR_ICMP_UNREACH)
break;
if (code == ICMP_FRAG_NEEDED) {
harderr = inet->pmtudisc != IP_PMTUDISC_DONT;
harderr = READ_ONCE(inet->pmtudisc) != IP_PMTUDISC_DONT;
err = EMSGSIZE;
} else {
err = icmp_err_convert[code].errno;

2
net/ipv4/udp.c
View File

@ -750,7 +750,7 @@ int __udp4_lib_err(struct sk_buff *skb, u32 info, struct udp_table *udptable)
case ICMP_DEST_UNREACH:
if (code == ICMP_FRAG_NEEDED) { /* Path MTU discovery */
ipv4_sk_update_pmtu(skb, sk, info);
if (inet->pmtudisc != IP_PMTUDISC_DONT) {
if (READ_ONCE(inet->pmtudisc) != IP_PMTUDISC_DONT) {
err = EMSGSIZE;
harderr = 1;
break;

2
net/netfilter/ipvs/ip_vs_sync.c
View File

@ -1335,7 +1335,7 @@ static void set_mcast_pmtudisc(struct sock *sk, int val)
/* setsockopt(sock, SOL_IP, IP_MTU_DISCOVER, &val, sizeof(val)); */
lock_sock(sk);
inet->pmtudisc = val;
WRITE_ONCE(inet->pmtudisc, val);
#ifdef CONFIG_IP_VS_IPV6
if (sk->sk_family == AF_INET6) {
struct ipv6_pinfo *np = inet6_sk(sk);