7b92493ab1
The SMR-protected inpcb lookup algorithm currently has to check whether
a matching inpcb belongs to a jail, in order to prioritize jailed
bound sockets. To do this it has to maintain a ucred reference, and for
this to be safe, the reference can't be released until the UMA
destructor is called, and this will not happen within any bounded time
period.
Changing SMR to periodically recycle garbage is not trivial. Instead,
let's implement SMR-synchronized lookup without needing to dereference
inp_cred. This will allow the inpcb code to free the inp_cred reference
immediately when a PCB is freed, ensuring that ucred (and thus jail)
references are released promptly.
Commit 220d892129 ("inpcb: immediately return matching pcb on lookup")
gets us part of the way there. This patch goes further to handle
lookups of unconnected sockets. Here, the strategy is to maintain a
well-defined order of items within a hash chain so that a wild lookup
can simply return the first match and preserve existing semantics. This
makes insertion of listening sockets more complicated in order to make
lookup simpler, which seems like the right tradeoff anyway given that
bind() is already a fairly expensive operation and lookups are more
common.
In particular, when inserting an unconnected socket, in_pcbinhash() now
keeps the following ordering:
- jailed sockets before non-jailed sockets,
- specified local addresses before unspecified local addresses.
Most of the change adds a separate SMR-based lookup path for inpcb hash
lookups. When a match is found, we try to lock the inpcb and
re-validate its connection info. In the common case, this works well
and we can simply return the inpcb. If this fails, typically because
something is concurrently modifying the inpcb, we go to the slow path,
which performs a serialized lookup.
Note, I did not touch lbgroup lookup, since there the credential
reference is formally synchronized by net_epoch, not SMR. In
particular, lbgroups are rarely allocated or freed.
I think it is possible to simplify in_pcblookup_hash_wild_locked() now,
but I didn't do it in this patch.
Discussed with: glebius
Tested by: glebius
Sponsored by: Klara, Inc.
Sponsored by: Modirum MDPay
Differential Revision: https://reviews.freebsd.org/D38572
69 lines
2.8 KiB
C
69 lines
2.8 KiB
C
/*-
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* SPDX-License-Identifier: BSD-3-Clause
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*
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* Copyright (c) 1982, 1986, 1990, 1993
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* The Regents of the University of California.
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* Copyright (c) 2010-2011 Juniper Networks, Inc.
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* All rights reserved.
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*
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* Portions of this software were developed by Robert N. M. Watson under
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* contract to Juniper Networks, Inc.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)in_pcb.h 8.1 (Berkeley) 6/10/93
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* $FreeBSD$
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*/
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#ifndef _NETINET_IN_PCB_VAR_H_
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#define _NETINET_IN_PCB_VAR_H_
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/*
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* Definitions shared between netinet/in_pcb.c and netinet6/in6_pcb.c
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*/
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VNET_DECLARE(uint32_t, in_pcbhashseed);
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#define V_in_pcbhashseed VNET(in_pcbhashseed)
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void inp_lock(struct inpcb *inp, const inp_lookup_t lock);
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void inp_unlock(struct inpcb *inp, const inp_lookup_t lock);
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int inp_trylock(struct inpcb *inp, const inp_lookup_t lock);
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bool inp_smr_lock(struct inpcb *, const inp_lookup_t);
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int in_pcb_lport(struct inpcb *, struct in_addr *, u_short *,
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struct ucred *, int);
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int in_pcb_lport_dest(struct inpcb *inp, struct sockaddr *lsa,
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u_short *lportp, struct sockaddr *fsa, u_short fport,
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struct ucred *cred, int lookupflags);
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struct inpcb * in_pcblookup_local(struct inpcbinfo *, struct in_addr, u_short,
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int, struct ucred *);
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struct inpcbport {
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struct inpcbhead phd_pcblist;
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CK_LIST_ENTRY(inpcbport) phd_hash;
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u_short phd_port;
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};
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#endif /* !_NETINET_IN_PCB_VAR_H_ */
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