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Fix deadlock in IPv6 PCB code.

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When several threads are trying to send datagram to the same destination,
but fragmentation is disabled and datagram size exceeds link MTU,
ip6_output() calls pfctlinput2(PRC_MSGSIZE). It does notify all
sockets wanted to know MTU to this destination. And since all threads
hold PCB lock while sending, taking the lock for each PCB in the
in6_pcbnotify() leads to deadlock.

RFC 3542 p.11.3 suggests notify all application wanted to receive
IPV6_PATHMTU ancillary data for each ICMPv6 packet too big message.
But it doesn't require this, when we don't receive ICMPv6 message.

Change ip6_notify_pmtu() function to be able use it directly from
ip6_output() to notify only one socket, and to notify all sockets
when ICMPv6 packet too big message received.

PR:		197059
Differential Revision:	https://reviews.freebsd.org/D1949
Reviewed by:	no objection from #network
Obtained from:	Yandex LLC
MFC after:	1 week
Sponsored by:	Yandex LLC
This commit is contained in:
ae 2015-03-04 11:20:01 +00:00
parent e5a77689c2
commit a312c1bedf
4 changed files with 25 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
sys/netinet6/in6_pcb.c
View File

@ -642,18 +642,12 @@ in6_pcbnotify(struct inpcbinfo *pcbinfo, struct sockaddr *dst,
/*
* If the error designates a new path MTU for a destination
* and the application (associated with this socket) wanted to
* know the value, notify. Note that we notify for all
* disconnected sockets if the corresponding application
* wanted. This is because some UDP applications keep sending
* sockets disconnected.
* know the value, notify.
* XXX: should we avoid to notify the value to TCP sockets?
*/
if (cmd == PRC_MSGSIZE && (inp->inp_flags & IN6P_MTU) != 0 &&
(IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) ||
IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, &sa6_dst->sin6_addr))) {
if (cmd == PRC_MSGSIZE)
ip6_notify_pmtu(inp, (struct sockaddr_in6 *)dst,
(u_int32_t *)cmdarg);
}
*(u_int32_t *)cmdarg);
/*
* Detect if we should notify the error. If no source and

29
sys/netinet6/ip6_input.c
View File

@ -1343,24 +1343,28 @@ ip6_savecontrol(struct inpcb *in6p, struct mbuf *m, struct mbuf **mp)
#undef IS2292
void
ip6_notify_pmtu(struct inpcb *in6p, struct sockaddr_in6 *dst, u_int32_t *mtu)
ip6_notify_pmtu(struct inpcb *inp, struct sockaddr_in6 *dst, u_int32_t mtu)
{
struct socket *so;
struct mbuf *m_mtu;
struct ip6_mtuinfo mtuctl;
so = in6p->inp_socket;
if (mtu == NULL)
KASSERT(inp != NULL, ("%s: inp == NULL", __func__));
/*
* Notify the error by sending IPV6_PATHMTU ancillary data if
* application wanted to know the MTU value.
* NOTE: we notify disconnected sockets, because some udp
* applications keep sending sockets disconnected.
* NOTE: our implementation doesn't notify connected sockets that has
* foreign address that is different than given destination addresses
* (this is permitted by RFC 3542).
*/
if ((inp->inp_flags & IN6P_MTU) == 0 || (
!IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_faddr) &&
!IN6_ARE_ADDR_EQUAL(&inp->in6p_faddr, &dst->sin6_addr)))
return;
#ifdef DIAGNOSTIC
if (so == NULL) /* I believe this is impossible */
panic("ip6_notify_pmtu: socket is NULL");
#endif
bzero(&mtuctl, sizeof(mtuctl)); /* zero-clear for safety */
mtuctl.ip6m_mtu = *mtu;
mtuctl.ip6m_mtu = mtu;
mtuctl.ip6m_addr = *dst;
if (sa6_recoverscope(&mtuctl.ip6m_addr))
return;
@ -1369,14 +1373,13 @@ ip6_notify_pmtu(struct inpcb *in6p, struct sockaddr_in6 *dst, u_int32_t *mtu)
IPV6_PATHMTU, IPPROTO_IPV6)) == NULL)
return;
so = inp->inp_socket;
if (sbappendaddr(&so->so_rcv, (struct sockaddr *)dst, NULL, m_mtu)
== 0) {
m_freem(m_mtu);
/* XXX: should count statistics */
} else
sorwakeup(so);
return;
}
#ifdef PULLDOWN_TEST

17
sys/netinet6/ip6_output.c
View File

@ -910,19 +910,12 @@ ip6_output(struct mbuf *m0, struct ip6_pktopts *opt,
* Even if the DONTFRAG option is specified, we cannot send the
* packet when the data length is larger than the MTU of the
* outgoing interface.
* Notify the error by sending IPV6_PATHMTU ancillary data as
* well as returning an error code (the latter is not described
* in the API spec.)
* Notify the error by sending IPV6_PATHMTU ancillary data if
* application wanted to know the MTU value. Also return an
* error code (this is not described in the API spec).
*/
u_int32_t mtu32;
struct ip6ctlparam ip6cp;
mtu32 = (u_int32_t)mtu;
bzero(&ip6cp, sizeof(ip6cp));
ip6cp.ip6c_cmdarg = (void *)&mtu32;
pfctlinput2(PRC_MSGSIZE, (struct sockaddr *)&ro_pmtu->ro_dst,
(void *)&ip6cp);
if (inp != NULL)
ip6_notify_pmtu(inp, &dst_sa, (u_int32_t)mtu);
error = EMSGSIZE;
goto bad;
}

3
sys/netinet6/ip6_var.h
View File

@ -368,8 +368,7 @@ int ip6_process_hopopts(struct mbuf *, u_int8_t *, int, u_int32_t *,
struct mbuf **ip6_savecontrol_v4(struct inpcb *, struct mbuf *,
struct mbuf **, int *);
void ip6_savecontrol(struct inpcb *, struct mbuf *, struct mbuf **);
void ip6_notify_pmtu(struct inpcb *, struct sockaddr_in6 *,
u_int32_t *);
void ip6_notify_pmtu(struct inpcb *, struct sockaddr_in6 *, u_int32_t);
int ip6_sysctl(int *, u_int, void *, size_t *, void *, size_t);
void ip6_forward(struct mbuf *, int);