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(1) bpf peer attaches to interface netif0
(2) Packet is received by netif0
(3) ifp->if_bpf pointer is checked and handed off to bpf
(4) bpf peer detaches from netif0 resulting in ifp->if_bpf being
initialized to NULL.
(5) ifp->if_bpf is dereferenced by bpf machinery
(6) Kaboom
This race condition likely explains the various different kernel panics
reported around sending SIGINT to tcpdump or dhclient processes. But really
this race can result in kernel panics anywhere you have frequent bpf attach
and detach operations with high packet per second load.
Summary of changes:
- Remove the bpf interface's "driverp" member
- When we attach bpf interfaces, we now set the ifp->if_bpf member to the
bpf interface structure. Once this is done, ifp->if_bpf should never be
NULL. [1]
- Introduce bpf_peers_present function, an inline operation which will do
a lockless read bpf peer list associated with the interface. It should
be noted that the bpf code will pickup the bpf_interface lock before adding
or removing bpf peers. This should serialize the access to the bpf descriptor
list, removing the race.
- Expose the bpf_if structure in bpf.h so that the bpf_peers_present function
can use it. This also removes the struct bpf_if; hack that was there.
- Adjust all consumers of the raw if_bpf structure to use bpf_peers_present
Now what happens is:
(1) Packet is received by netif0
(2) Check to see if bpf descriptor list is empty
(3) Pickup the bpf interface lock
(4) Hand packet off to process
From the attach/detach side:
(1) Pickup the bpf interface lock
(2) Add/remove from bpf descriptor list
Now that we are storing the bpf interface structure with the ifnet, there is
is no need to walk the bpf interface list to locate the correct bpf interface.
We now simply look up the interface, and initialize the pointer. This has a
nice side effect of changing a bpf interface attach operation from O(N) (where
N is the number of bpf interfaces), to O(1).
[1] From now on, we can no longer check ifp->if_bpf to tell us whether or
not we have any bpf peers that might be interested in receiving packets.
In collaboration with: sam@
MFC after: 1 month
147 lines
5.3 KiB
C
147 lines
5.3 KiB
C
/*-
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* Copyright (c) 1990, 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from the Stanford/CMU enet packet filter,
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* (net/enet.c) distributed as part of 4.3BSD, and code contributed
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* to Berkeley by Steven McCanne and Van Jacobson both of Lawrence
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* Berkeley Laboratory.
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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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* 4. 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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* @(#)bpfdesc.h 8.1 (Berkeley) 6/10/93
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*
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* $FreeBSD$
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*/
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#ifndef _NET_BPFDESC_H_
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#define _NET_BPFDESC_H_
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#include <sys/callout.h>
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#include <sys/selinfo.h>
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#include <sys/queue.h>
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#include <sys/conf.h>
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#include <net/if.h>
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/*
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* Descriptor associated with each open bpf file.
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*/
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struct bpf_d {
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LIST_ENTRY(bpf_d) bd_next; /* Linked list of descriptors */
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/*
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* Buffer slots: two mbuf clusters buffer the incoming packets.
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* The model has three slots. Sbuf is always occupied.
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* sbuf (store) - Receive interrupt puts packets here.
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* hbuf (hold) - When sbuf is full, put cluster here and
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* wakeup read (replace sbuf with fbuf).
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* fbuf (free) - When read is done, put cluster here.
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* On receiving, if sbuf is full and fbuf is 0, packet is dropped.
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*/
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caddr_t bd_sbuf; /* store slot */
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caddr_t bd_hbuf; /* hold slot */
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caddr_t bd_fbuf; /* free slot */
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int bd_slen; /* current length of store buffer */
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int bd_hlen; /* current length of hold buffer */
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int bd_bufsize; /* absolute length of buffers */
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struct bpf_if * bd_bif; /* interface descriptor */
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u_long bd_rtout; /* Read timeout in 'ticks' */
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struct bpf_insn *bd_rfilter; /* read filter code */
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struct bpf_insn *bd_wfilter; /* write filter code */
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#ifdef BPF_JITTER
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bpf_jit_filter *bd_bfilter; /* binary filter code */
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#endif
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u_long bd_rcount; /* number of packets received */
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u_long bd_dcount; /* number of packets dropped */
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u_char bd_promisc; /* true if listening promiscuously */
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u_char bd_state; /* idle, waiting, or timed out */
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u_char bd_immediate; /* true to return on packet arrival */
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int bd_hdrcmplt; /* false to fill in src lladdr automatically */
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int bd_seesent; /* true if bpf should see sent packets */
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int bd_async; /* non-zero if packet reception should generate signal */
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int bd_sig; /* signal to send upon packet reception */
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struct sigio * bd_sigio; /* information for async I/O */
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#if BSD < 199103
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u_char bd_selcoll; /* true if selects collide */
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int bd_timedout;
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struct thread * bd_selthread; /* process that last selected us */
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#else
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u_char bd_pad; /* explicit alignment */
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struct selinfo bd_sel; /* bsd select info */
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#endif
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struct mtx bd_mtx; /* mutex for this descriptor */
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struct callout bd_callout; /* for BPF timeouts with select */
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struct label *bd_label; /* MAC label for descriptor */
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u_long bd_fcount; /* number of packets which matched filter */
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pid_t bd_pid; /* PID which created descriptor */
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int bd_locked; /* true if descriptor is locked */
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};
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/* Values for bd_state */
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#define BPF_IDLE 0 /* no select in progress */
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#define BPF_WAITING 1 /* waiting for read timeout in select */
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#define BPF_TIMED_OUT 2 /* read timeout has expired in select */
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#define BPFD_LOCK(bd) mtx_lock(&(bd)->bd_mtx)
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#define BPFD_UNLOCK(bd) mtx_unlock(&(bd)->bd_mtx)
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#define BPFD_LOCK_ASSERT(bd) do { \
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mtx_assert(&(bd)->bd_mtx, MA_OWNED); \
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NET_ASSERT_GIANT(); \
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} while (0)
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/* Test whether a BPF is ready for read(). */
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#define bpf_ready(bd) \
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((bd)->bd_hlen != 0 || \
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(((bd)->bd_immediate || (bd)->bd_state == BPF_TIMED_OUT) && \
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(bd)->bd_slen != 0))
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/*
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* External representation of the bpf descriptor
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*/
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struct xbpf_d {
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u_char bd_promisc;
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u_char bd_immediate;
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int bd_hdrcmplt;
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int bd_seesent;
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int bd_async;
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u_long bd_rcount;
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u_long bd_dcount;
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u_long bd_fcount;
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int bd_sig;
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int bd_slen;
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int bd_hlen;
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int bd_bufsize;
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pid_t bd_pid;
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char bd_ifname[IFNAMSIZ];
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int bd_locked;
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};
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#define BPFIF_LOCK(bif) mtx_lock(&(bif)->bif_mtx)
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#define BPFIF_UNLOCK(bif) mtx_unlock(&(bif)->bif_mtx)
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#endif
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