@@ -1222,6 +1222,7 @@ struct proto {
int (*connect)(struct sock *sk,
struct sockaddr *uaddr,
int addr_len);
+ void (*set_rcv_saddr)(struct sock *sk, void *addr);
int (*disconnect)(struct sock *sk, int flags);
struct sock * (*accept)(struct sock *sk,
@@ -1263,7 +1264,6 @@ struct proto {
/* Keeping track of sk's, looking them up, and port selection methods. */
int (*hash)(struct sock *sk);
void (*unhash)(struct sock *sk);
- void (*rehash)(struct sock *sk);
int (*get_port)(struct sock *sk, unsigned short snum);
void (*put_port)(struct sock *sk);
#ifdef CONFIG_BPF_SYSCALL
@@ -193,7 +193,6 @@ static inline int udp_lib_hash(struct sock *sk)
}
void udp_lib_unhash(struct sock *sk);
-void udp_lib_rehash(struct sock *sk, u16 new_hash);
static inline void udp_lib_close(struct sock *sk, long timeout)
{
@@ -286,6 +285,8 @@ int udp_rcv(struct sk_buff *skb);
int udp_ioctl(struct sock *sk, int cmd, int *karg);
int udp_init_sock(struct sock *sk);
int udp_pre_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
+void udp_lib_set_rcv_saddr(struct sock *sk, void *addr, u16 hash);
+int udp_set_rcv_saddr(struct sock *sk, void *addr);
int __udp_disconnect(struct sock *sk, int flags);
int udp_disconnect(struct sock *sk, int flags);
__poll_t udp_poll(struct file *file, struct socket *sock, poll_table *wait);
@@ -643,8 +643,17 @@ static int sock_bindtoindex_locked(struct sock *sk, int ifindex)
/* Paired with all READ_ONCE() done locklessly. */
WRITE_ONCE(sk->sk_bound_dev_if, ifindex);
- if (sk->sk_prot->rehash)
- sk->sk_prot->rehash(sk);
+ /* Force rehash if protocol needs it */
+ if (sk->sk_prot->set_rcv_saddr) {
+ if (IS_ENABLED(CONFIG_IPV6) && sk->sk_family == AF_INET6) {
+ sk->sk_prot->set_rcv_saddr(sk, &sk->sk_v6_rcv_saddr);
+ } else if (sk->sk_family == AF_INET) {
+ struct inet_sock *inet = inet_sk(sk);
+
+ sk->sk_prot->set_rcv_saddr(sk, &inet->inet_rcv_saddr);
+ }
+ }
+
sk_dst_reset(sk);
ret = 0;
@@ -64,9 +64,10 @@ int __ip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
if (!inet->inet_saddr)
inet->inet_saddr = fl4->saddr; /* Update source address */
if (!inet->inet_rcv_saddr) {
- inet->inet_rcv_saddr = fl4->saddr;
- if (sk->sk_prot->rehash && sk->sk_family == AF_INET)
- sk->sk_prot->rehash(sk);
+ if (sk->sk_prot->set_rcv_saddr && sk->sk_family == AF_INET)
+ sk->sk_prot->set_rcv_saddr(sk, &fl4->saddr);
+ else
+ inet->inet_rcv_saddr = fl4->saddr;
}
inet->inet_daddr = fl4->daddr;
inet->inet_dport = usin->sin_port;
@@ -486,10 +486,13 @@ struct sock *__udp4_lib_lookup(const struct net *net, __be32 saddr,
int sdif, struct udp_table *udptable, struct sk_buff *skb)
{
unsigned short hnum = ntohs(dport);
+ struct udp_hslot *hslot, *hslot2;
unsigned int hash2, slot2;
- struct udp_hslot *hslot2;
struct sock *result, *sk;
+ hslot = udp_hashslot(udptable, net, hnum);
+ spin_lock_bh(&hslot->lock);
+
hash2 = ipv4_portaddr_hash(net, daddr, hnum);
slot2 = hash2 & udptable->mask;
hslot2 = &udptable->hash2[slot2];
@@ -526,6 +529,8 @@ struct sock *__udp4_lib_lookup(const struct net *net, __be32 saddr,
htonl(INADDR_ANY), hnum, dif, sdif,
hslot2, skb);
done:
+ spin_unlock_bh(&hslot->lock);
+
if (IS_ERR(result))
return NULL;
return result;
@@ -1948,10 +1953,12 @@ int __udp_disconnect(struct sock *sk, int flags)
sock_rps_reset_rxhash(sk);
sk->sk_bound_dev_if = 0;
if (!(sk->sk_userlocks & SOCK_BINDADDR_LOCK)) {
+ if (sk->sk_prot->set_rcv_saddr &&
+ (sk->sk_userlocks & SOCK_BINDPORT_LOCK)) {
+ sk->sk_prot->set_rcv_saddr(sk, &(__be32){ 0 });
+ }
+
inet_reset_saddr(sk);
- if (sk->sk_prot->rehash &&
- (sk->sk_userlocks & SOCK_BINDPORT_LOCK))
- sk->sk_prot->rehash(sk);
}
if (!(sk->sk_userlocks & SOCK_BINDPORT_LOCK)) {
@@ -2000,25 +2007,36 @@ void udp_lib_unhash(struct sock *sk)
}
EXPORT_SYMBOL(udp_lib_unhash);
-/*
- * inet_rcv_saddr was changed, we must rehash secondary hash
+/**
+ * udp_lib_set_rcv_saddr() - Set local address and rehash socket atomically
+ * @sk: Socket changing local address
+ * @addr: New address, __be32 * or struct in6_addr * depending on family
+ * @hash: New secondary hash (port + local address) for socket
+ *
+ * Set local address for socket and rehash it while holding a spinlock on the
+ * primary hash chain (port only). This needs to be atomic to avoid that a
+ * concurrent lookup misses a socket while it's being connected or disconnected.
*/
-void udp_lib_rehash(struct sock *sk, u16 newhash)
+void udp_lib_set_rcv_saddr(struct sock *sk, void *addr, u16 hash)
{
+ struct udp_hslot *hslot;
+
if (sk_hashed(sk)) {
struct udp_table *udptable = udp_get_table_prot(sk);
- struct udp_hslot *hslot, *hslot2, *nhslot2;
+ struct udp_hslot *hslot2, *nhslot2;
hslot2 = udp_hashslot2(udptable, udp_sk(sk)->udp_portaddr_hash);
- nhslot2 = udp_hashslot2(udptable, newhash);
- udp_sk(sk)->udp_portaddr_hash = newhash;
+ nhslot2 = udp_hashslot2(udptable, hash);
+
+ hslot = udp_hashslot(udptable, sock_net(sk),
+ udp_sk(sk)->udp_port_hash);
+
+ spin_lock_bh(&hslot->lock);
+
+ udp_sk(sk)->udp_portaddr_hash = hash;
if (hslot2 != nhslot2 ||
rcu_access_pointer(sk->sk_reuseport_cb)) {
- hslot = udp_hashslot(udptable, sock_net(sk),
- udp_sk(sk)->udp_port_hash);
- /* we must lock primary chain too */
- spin_lock_bh(&hslot->lock);
if (rcu_access_pointer(sk->sk_reuseport_cb))
reuseport_detach_sock(sk);
@@ -2034,20 +2052,32 @@ void udp_lib_rehash(struct sock *sk, u16 newhash)
nhslot2->count++;
spin_unlock(&nhslot2->lock);
}
-
- spin_unlock_bh(&hslot->lock);
}
}
+
+ if (sk->sk_family == AF_INET)
+ sk->sk_rcv_saddr = *(__be32 *)addr;
+ else if (sk->sk_family == AF_INET6)
+ sk->sk_v6_rcv_saddr = *(struct in6_addr *)addr;
+
+ if (sk_hashed(sk))
+ spin_unlock_bh(&hslot->lock);
}
-EXPORT_SYMBOL(udp_lib_rehash);
+EXPORT_SYMBOL(udp_lib_set_rcv_saddr);
-void udp_v4_rehash(struct sock *sk)
+/**
+ * udp_v4_set_rcv_saddr() - Set local address and new hash for IPv4 socket
+ * @sk: Socket changing local address
+ * @addr: New address, pointer to __be32 representation
+ */
+void udp_v4_set_rcv_saddr(struct sock *sk, void *addr)
{
- u16 new_hash = ipv4_portaddr_hash(sock_net(sk),
- inet_sk(sk)->inet_rcv_saddr,
- inet_sk(sk)->inet_num);
- udp_lib_rehash(sk, new_hash);
+ u16 hash = ipv4_portaddr_hash(sock_net(sk),
+ *(__be32 *)addr, inet_sk(sk)->inet_num);
+
+ udp_lib_set_rcv_saddr(sk, addr, hash);
}
+EXPORT_SYMBOL(udp_v4_set_rcv_saddr);
static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{
@@ -2941,6 +2971,7 @@ struct proto udp_prot = {
.close = udp_lib_close,
.pre_connect = udp_pre_connect,
.connect = ip4_datagram_connect,
+ .set_rcv_saddr = udp_v4_set_rcv_saddr,
.disconnect = udp_disconnect,
.ioctl = udp_ioctl,
.init = udp_init_sock,
@@ -2953,7 +2984,6 @@ struct proto udp_prot = {
.release_cb = ip4_datagram_release_cb,
.hash = udp_lib_hash,
.unhash = udp_lib_unhash,
- .rehash = udp_v4_rehash,
.get_port = udp_v4_get_port,
.put_port = udp_lib_unhash,
#ifdef CONFIG_BPF_SYSCALL
@@ -10,7 +10,7 @@ int __udp4_lib_rcv(struct sk_buff *, struct udp_table *, int);
int __udp4_lib_err(struct sk_buff *, u32, struct udp_table *);
int udp_v4_get_port(struct sock *sk, unsigned short snum);
-void udp_v4_rehash(struct sock *sk);
+void udp_v4_set_rcv_saddr(struct sock *sk, void *addr);
int udp_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
unsigned int optlen);
@@ -57,7 +57,7 @@ struct proto udplite_prot = {
.recvmsg = udp_recvmsg,
.hash = udp_lib_hash,
.unhash = udp_lib_unhash,
- .rehash = udp_v4_rehash,
+ .set_rcv_saddr = udp_v4_set_rcv_saddr,
.get_port = udp_v4_get_port,
.memory_allocated = &udp_memory_allocated,
@@ -104,10 +104,19 @@ int ip6_datagram_dst_update(struct sock *sk, bool fix_sk_saddr)
np->saddr = fl6.saddr;
if (ipv6_addr_any(&sk->sk_v6_rcv_saddr)) {
- sk->sk_v6_rcv_saddr = fl6.saddr;
- inet->inet_rcv_saddr = LOOPBACK4_IPV6;
- if (sk->sk_prot->rehash)
- sk->sk_prot->rehash(sk);
+ __be32 v4addr = LOOPBACK4_IPV6;
+
+ if (sk->sk_prot->set_rcv_saddr &&
+ sk->sk_family == AF_INET)
+ sk->sk_prot->set_rcv_saddr(sk, &v4addr);
+ else
+ inet->inet_rcv_saddr = v4addr;
+
+ if (sk->sk_prot->set_rcv_saddr &&
+ sk->sk_family == AF_INET6)
+ sk->sk_prot->set_rcv_saddr(sk, &fl6.saddr);
+ else
+ sk->sk_v6_rcv_saddr = fl6.saddr;
}
}
@@ -209,10 +218,15 @@ int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
if (ipv6_addr_any(&sk->sk_v6_rcv_saddr) ||
ipv6_mapped_addr_any(&sk->sk_v6_rcv_saddr)) {
- ipv6_addr_set_v4mapped(inet->inet_rcv_saddr,
- &sk->sk_v6_rcv_saddr);
- if (sk->sk_prot->rehash && sk->sk_family == AF_INET6)
- sk->sk_prot->rehash(sk);
+ struct in6_addr v4mapped;
+
+ ipv6_addr_set_v4mapped(inet->inet_rcv_saddr, &v4mapped);
+
+ if (sk->sk_prot->set_rcv_saddr &&
+ sk->sk_family == AF_INET6)
+ sk->sk_prot->set_rcv_saddr(sk, &v4mapped);
+ else
+ sk->sk_v6_rcv_saddr = v4mapped;
}
goto out;
@@ -105,14 +105,19 @@ int udp_v6_get_port(struct sock *sk, unsigned short snum)
return udp_lib_get_port(sk, snum, hash2_nulladdr);
}
-void udp_v6_rehash(struct sock *sk)
+/**
+ * udp_v6_set_rcv_saddr() - Set local address and new hash for IPv6 socket
+ * @sk: Socket changing local address
+ * @addr: New address, pointer to struct in6_addr
+ */
+void udp_v6_set_rcv_saddr(struct sock *sk, void *addr)
{
- u16 new_hash = ipv6_portaddr_hash(sock_net(sk),
- &sk->sk_v6_rcv_saddr,
- inet_sk(sk)->inet_num);
+ u16 hash = ipv6_portaddr_hash(sock_net(sk),
+ addr, inet_sk(sk)->inet_num);
- udp_lib_rehash(sk, new_hash);
+ udp_lib_set_rcv_saddr(sk, addr, hash);
}
+EXPORT_SYMBOL(udp_v6_set_rcv_saddr);
static int compute_score(struct sock *sk, const struct net *net,
const struct in6_addr *saddr, __be16 sport,
@@ -1765,6 +1770,7 @@ struct proto udpv6_prot = {
.close = udp_lib_close,
.pre_connect = udpv6_pre_connect,
.connect = ip6_datagram_connect,
+ .set_rcv_saddr = udp_v6_set_rcv_saddr,
.disconnect = udp_disconnect,
.ioctl = udp_ioctl,
.init = udpv6_init_sock,
@@ -1777,7 +1783,6 @@ struct proto udpv6_prot = {
.release_cb = ip6_datagram_release_cb,
.hash = udp_lib_hash,
.unhash = udp_lib_unhash,
- .rehash = udp_v6_rehash,
.get_port = udp_v6_get_port,
.put_port = udp_lib_unhash,
#ifdef CONFIG_BPF_SYSCALL
@@ -14,7 +14,7 @@ int __udp6_lib_err(struct sk_buff *, struct inet6_skb_parm *, u8, u8, int,
int udpv6_init_sock(struct sock *sk);
int udp_v6_get_port(struct sock *sk, unsigned short snum);
-void udp_v6_rehash(struct sock *sk);
+void udp_v6_set_rcv_saddr(struct sock *sk, void *addr);
int udpv6_getsockopt(struct sock *sk, int level, int optname,
char __user *optval, int __user *optlen);
@@ -56,7 +56,7 @@ struct proto udplitev6_prot = {
.recvmsg = udpv6_recvmsg,
.hash = udp_lib_hash,
.unhash = udp_lib_unhash,
- .rehash = udp_v6_rehash,
+ .set_rcv_saddr = udp_v6_set_rcv_saddr,
.get_port = udp_v6_get_port,
.memory_allocated = &udp_memory_allocated,
If a UDP socket changes its local address while it's receiving datagrams, as a result of connect(), there is a period during which a lookup operation might fail to find it, after the address is changed but before the secondary hash (port and address) is updated. Secondary hash chains were introduced by commit 30fff9231fad ("udp: bind() optimisation") and, as a result, a rehash operation became needed to make a bound socket reachable again after a connect(). This operation was introduced by commit 719f835853a9 ("udp: add rehash on connect()") which isn't however a complete fix: the socket will be found once the rehashing completes, but not while it's pending. This is noticeable with a socat(1) server in UDP4-LISTEN mode, and a client sending datagrams to it. After the server receives the first datagram (cf. _xioopen_ipdgram_listen()), it issues a connect() to the address of the sender, in order to set up a directed flow. Now, if the client, running on a different CPU thread, happens to send a (subsequent) datagram while the server's socket changes its address, but is not rehashed yet, this will result in a failed lookup and a port unreachable error delivered to the client, as apparent from the following reproducer: LEN=$(($(cat /proc/sys/net/core/wmem_default) / 4)) dd if=/dev/urandom bs=1 count=${LEN} of=tmp.in while :; do taskset -c 1 socat UDP4-LISTEN:1337,null-eof OPEN:tmp.out,create,trunc & sleep 0.1 || sleep 1 taskset -c 2 socat OPEN:tmp.in UDP4:localhost:1337,shut-null wait done where the client will eventually get ECONNREFUSED on a write() (typically the second or third one of a given iteration): 2024/11/13 21:28:23 socat[46901] E write(6, 0x556db2e3c000, 8192): Connection refused This issue was first observed as a seldom failure in Podman's tests checking UDP functionality while using pasta(1) to connect the container's network namespace, which leads us to a reproducer with the lookup error resulting in an ICMP packet on a tap device: LOCAL_ADDR="$(ip -j -4 addr show|jq -rM '.[] | .addr_info[0] | select(.scope == "global").local')" while :; do ./pasta --config-net -p pasta.pcap -u 1337 socat UDP4-LISTEN:1337,null-eof OPEN:tmp.out,create,trunc & sleep 0.2 || sleep 1 socat OPEN:tmp.in UDP4:${LOCAL_ADDR}:1337,shut-null wait cmp tmp.in tmp.out done Once this fails: tmp.in tmp.out differ: char 8193, line 29 we can finally have a look at what's going on: $ tshark -r pasta.pcap 1 0.000000 :: ? ff02::16 ICMPv6 110 Multicast Listener Report Message v2 2 0.168690 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192 3 0.168767 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192 4 0.168806 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192 5 0.168827 c6:47:05:8d:dc:04 ? Broadcast ARP 42 Who has 88.198.0.161? Tell 88.198.0.164 6 0.168851 9a:55:9a:55:9a:55 ? c6:47:05:8d:dc:04 ARP 42 88.198.0.161 is at 9a:55:9a:55:9a:55 7 0.168875 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192 8 0.168896 88.198.0.164 ? 88.198.0.161 ICMP 590 Destination unreachable (Port unreachable) 9 0.168926 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192 10 0.168959 88.198.0.161 ? 88.198.0.164 UDP 8234 60260 ? 1337 Len=8192 11 0.168989 88.198.0.161 ? 88.198.0.164 UDP 4138 60260 ? 1337 Len=4096 12 0.169010 88.198.0.161 ? 88.198.0.164 UDP 42 60260 ? 1337 Len=0 On the third datagram received, the network namespace of the container initiates an ARP lookup to deliver the ICMP message. In another variant of this reproducer, starting the client with: strace -f pasta --config-net -u 1337 socat UDP4-LISTEN:1337,null-eof OPEN:tmp.out,create,trunc 2>strace.log & and connecting to the socat server using a loopback address: socat OPEN:tmp.in UDP4:localhost:1337,shut-null we can more clearly observe a sendmmsg() call failing after the first datagram is delivered: [pid 278012] connect(173, 0x7fff96c95fc0, 16) = 0 [...] [pid 278012] recvmmsg(173, 0x7fff96c96020, 1024, MSG_DONTWAIT, NULL) = -1 EAGAIN (Resource temporarily unavailable) [pid 278012] sendmmsg(173, 0x561c5ad0a720, 1, MSG_NOSIGNAL) = 1 [...] [pid 278012] sendmmsg(173, 0x561c5ad0a720, 1, MSG_NOSIGNAL) = -1 ECONNREFUSED (Connection refused) and, somewhat confusingly, after a connect() on the same socket succeeded. To fix this, replace the rehash operation by a set_rcv_saddr() callback holding the spinlock on the primary hash chain, just like the rehash operation used to do, but also setting the address while holding the spinlock. To make this atomic against the lookup operation, also acquire the spinlock on the primary chain there. This results in some awkwardness at a caller site, specifically sock_bindtoindex_locked(), where we really just need to rehash the socket without changing its address. With the new operation, we now need to forcibly set the current address again. On the other hand, this appears more elegant than alternatives such as fetching the spinlock reference in ip4_datagram_connect() and ip6_datagram_conect(), and keeping the rehash operation around for a single user also seems a tad overkill. Reported-by: Ed Santiago <santiago@redhat.com> Link: https://github.com/containers/podman/issues/24147 Analysed-by: David Gibson <david@gibson.dropbear.id.au> Fixes: 30fff9231fad ("udp: bind() optimisation") Signed-off-by: Stefano Brivio <sbrivio@redhat.com> --- include/net/sock.h | 2 +- include/net/udp.h | 3 +- net/core/sock.c | 13 ++++++-- net/ipv4/datagram.c | 7 +++-- net/ipv4/udp.c | 76 +++++++++++++++++++++++++++++++-------------- net/ipv4/udp_impl.h | 2 +- net/ipv4/udplite.c | 2 +- net/ipv6/datagram.c | 30 +++++++++++++----- net/ipv6/udp.c | 17 ++++++---- net/ipv6/udp_impl.h | 2 +- net/ipv6/udplite.c | 2 +- 11 files changed, 108 insertions(+), 48 deletions(-)