The first one never triggers because bpf_canfreebuf() can only be true for
zero-copy buffers and zero-copy buffers are not read with read(2).
The second also never triggers, because we check the free buffer before
calling ROTATE_BUFFERS(). If the hold buffer is in use the free buffer
will be NULL and there is nothing else to do besides drop the packet. If
the free buffer isn't NULL the hold buffer _is_ free and it is safe to
rotate the buffers.
Update the comment in ROTATE_BUFFERS macro to match the logic described
here.
While here fix a few typos in comments.
MFC after: 2 weeks
Sponsored by: Rubicon Communications (Netgate)
A couple of fields are still exposed via struct bpf_if_ext so that
bpf_peers_present() can be inlined into its callers. However, this change
eliminates some type duplication in the resulting CTF container, since
otherwise ctfmerge(1) propagates the duplication through all types that
contain a struct bpf_if.
Differential Revision: https://reviews.freebsd.org/D2319
Reviewed by: melifaro, rpaulo
bpf(4) and vlan(4) related event declarations to bpf.h and
if_vlan_var.h. To avoid dependency on eventhandler.h, protect
these declarations with ifdef SYS_EVENTHANDLER_H.
Sponsored by: Netflix
Sponsored by: Nginx, Inc.
cause kernel panics.
Add a flag to the bpf descriptor to indicate whether the hold buffer
is in use. In bpfread(), set the "hold buffer in use" flag before
dropping the descriptor lock during the call to bpf_uiomove().
Everywhere else the hold buffer is used or changed, wait while
the hold buffer is in use by bpfread(). Add a KASSERT in bpfread()
after re-acquiring the descriptor lock to assist uncovering any
additional hold buffer races.
'flags' field is added to the end of bpf_if structure. Currently the only
flag is BPFIF_FLAG_DYING which is set on bpf detach and checked by bpf_attachd()
Problem can be easily triggered on SMP stable/[89] by the following command (sort of):
'while true; do ifconfig vlan222 create vlan 222 vlandev em0 up ; tcpdump -pi vlan222 & ; ifconfig vlan222 destroy ; done'
Fix possible use-after-free when BPF detaches itself from interface, freeing bpf_bif memory,
while interface is still UP and there can be routes via this interface.
Freeing is now delayed till ifnet_departure_event is received via eventhandler(9) api.
Convert bpfd rwlock back to mutex due lack of performance gain (currently checking if packet
matches filter is done without holding bpfd lock and we have to acquire write lock if packet matches)
Approved by: kib(mentor)
MFC in: 4 weeks
Linux and Solaris (at least OpenSolaris) has PF_PACKET socket families to send
raw ethernet frames. The only FreeBSD interface that can be used to send raw frames
is BPF. As a result, many programs like cdpd, lldpd, various dhcp stuff uses
BPF only to send data. This leads us to the situation when software like cdpd,
being run on high-traffic-volume interface significantly reduces overall performance
since we have to acquire additional locks for every packet.
Here we add sysctl that changes BPF behavior in the following way:
If program came and opens BPF socket without explicitly specifyin read filter we
assume it to be write-only and add it to special writer-only per-interface list.
This makes bpf_peers_present() return 0, so no additional overhead is introduced.
After filter is supplied, descriptor is added to original per-interface list permitting
packets to be captured.
Unfortunately, pcap_open_live() sets catch-all filter itself for the purpose of
setting snap length.
Fortunately, most programs explicitly sets (event catch-all) filter after that.
tcpdump(1) is a good example.
So a bit hackis approach is taken: we upgrade description only after second
BIOCSETF is received.
Sysctl is named net.bpf.optimize_writers and is turned off by default.
- While here, document all sysctl variables in bpf.4
Sponsored by Yandex LLC
Reviewed by: glebius (previous version)
Reviewed by: silence on -net@
Approved by: (mentor)
MFC after: 4 weeks
Interface locks and descriptor locks are converted from mutex(9) to rwlock(9).
This greately improves performance: in most common case we need to acquire 1
reader lock instead of 2 mutexes.
- Remove filter(descriptor) (reader) lock in bpf_mtap[2]
This was suggested by glebius@. We protect filter by requesting interface
writer lock on filter change.
- Cover struct bpf_if under BPF_INTERNAL define. This permits including bpf.h
without including rwlock stuff. However, this is is temporary solution,
struct bpf_if should be made opaque for any external caller.
Found by: Dmitrij Tejblum <tejblum@yandex-team.ru>
Sponsored by: Yandex LLC
Reviewed by: glebius (previous version)
Reviewed by: silence on -net@
Approved by: (mentor)
MFC after: 3 weeks
aspect of time stamp configuration per interface rather than per BPF
descriptor. Prior to this, the order in which BPF devices were opened and the
per descriptor time stamp configuration settings could cause non-deterministic
and unintended behaviour with respect to time stamping. With the new scheme, a
BPF attached interface's tscfg sysctl entry can be set to "default", "none",
"fast", "normal" or "external". Setting "default" means use the system default
option (set with the net.bpf.tscfg.default sysctl), "none" means do not
generate time stamps for tapped packets, "fast" means generate time stamps for
tapped packets using a hz granularity system clock read, "normal" means
generate time stamps for tapped packets using a full timecounter granularity
system clock read and "external" (currently unimplemented) means use the time
stamp provided with the packet from an underlying source.
- Utilise the recently introduced sysclock_getsnapshot() and
sysclock_snap2bintime() KPIs to ensure the system clock is only read once per
packet, regardless of the number of BPF descriptors and time stamp formats
requested. Use the per BPF attached interface time stamp configuration to
control if sysclock_getsnapshot() is called and whether the system clock read
is fast or normal. The per BPF descriptor time stamp configuration is then
used to control how the system clock snapshot is converted to a bintime by
sysclock_snap2bintime().
- Remove all FAST related BPF descriptor flag variants. Performing a "fast"
read of the system clock is now controlled per BPF attached interface using
the net.bpf.tscfg sysctl tree.
- Update the bpf.4 man page.
Committed on behalf of Julien Ridoux and Darryl Veitch from the University of
Melbourne, Australia, as part of the FreeBSD Foundation funded "Feed-Forward
Clock Synchronization Algorithms" project.
For more information, see http://www.synclab.org/radclock/
In collaboration with: Julien Ridoux (jridoux at unimelb edu au)
contain both a regular timestamp obtained from the system clock and the
current feed-forward ffcounter value. This enables new possibilities including
comparison of timekeeping performance and timestamp correction during post
processing.
- Add the net.bpf.ffclock_tstamp sysctl to provide a choice between timestamping
packets using the feedback or feed-forward system clock.
Committed on behalf of Julien Ridoux and Darryl Veitch from the University of
Melbourne, Australia, as part of the FreeBSD Foundation funded "Feed-Forward
Clock Synchronization Algorithms" project.
For more information, see http://www.synclab.org/radclock/
Submitted by: Julien Ridoux (jridoux at unimelb edu au)
- Allow setting format, resolution and accuracy of BPF time stamps per
listener. Previously, we were only able to use microtime(9). Now we can
set various resolutions and accuracies with ioctl(2) BIOCSTSTAMP command.
Similarly, we can get the current resolution and accuracy with BIOCGTSTAMP
command. Document all supported options in bpf(4) and their uses.
- Introduce new time stamp 'struct bpf_ts' and header 'struct bpf_xhdr'.
The new time stamp has both 64-bit second and fractional parts. bpf_xhdr
has this time stamp instead of 'struct timeval' for bh_tstamp. The new
structures let us use bh_tstamp of same size on both 32-bit and 64-bit
platforms without adding additional shims for 32-bit binaries. On 64-bit
platforms, size of BPF header does not change compared to bpf_hdr as its
members are already all 64-bit long. On 32-bit platforms, the size may
increase by 8 bytes. For backward compatibility, struct bpf_hdr with
struct timeval is still the default header unless new time stamp format is
explicitly requested. However, the behaviour may change in the future and
all relevant code is wrapped around "#ifdef BURN_BRIDGES" for now.
- Add experimental support for tagging mbufs with time stamps from a lower
layer, e.g., device driver. Currently, mbuf_tags(9) is used to tag mbufs.
The time stamps must be uptime in 'struct bintime' format as binuptime(9)
and getbinuptime(9) do.
Reviewed by: net@
just like BIOCSETF but it doesn't drop all the packets buffered on
the discriptor and reset the statistics.
Also, when setting the write filter, don't drop packets waiting to
be read or reset the statistics.
PR: 118486
Submitted by: Matthew Luckie <mluckie@cs.waikato.ac.nz>
MFC after: 1 month
overhead of packet capture by allowing a user process to directly "loan"
buffer memory to the kernel rather than using read(2) to explicitly copy
data from kernel address space.
The user process will issue new BPF ioctls to set the shared memory
buffer mode and provide pointers to buffers and their size. The kernel
then wires and maps the pages into kernel address space using sf_buf(9),
which on supporting architectures will use the direct map region. The
current "buffered" access mode remains the default, and support for
zero-copy buffers must, for the time being, be explicitly enabled using
a sysctl for the kernel to accept requests to use it.
The kernel and user process synchronize use of the buffers with atomic
operations, avoiding the need for system calls under load; the user
process may use select()/poll()/kqueue() to manage blocking while
waiting for network data if the user process is able to consume data
faster than the kernel generates it. Patchs to libpcap are available
to allow libpcap applications to transparently take advantage of this
support. Detailed information on the new API may be found in bpf(4),
including specific atomic operations and memory barriers required to
synchronize buffer use safely.
These changes modify the base BPF implementation to (roughly) abstrac
the current buffer model, allowing the new shared memory model to be
added, and add new monitoring statistics for netstat to print. The
implementation, with the exception of some monitoring hanges that break
the netstat monitoring ABI for BPF, will be MFC'd.
Zerocopy bpf buffers are still considered experimental are disabled
by default. To experiment with this new facility, adjust the
net.bpf.zerocopy_enable sysctl variable to 1.
Changes to libpcap will be made available as a patch for the time being,
and further refinements to the implementation are expected.
Sponsored by: Seccuris Inc.
In collaboration with: rwatson
Tested by: pwood, gallatin
MFC after: 4 months [1]
[1] Certain portions will probably not be MFCed, specifically things
that can break the monitoring ABI.
- BIOCGDIRECTION and BIOCSDIRECTION get or set the setting determining
whether incoming, outgoing, or all packets on the interface should be
returned by BPF. Set to BPF_D_IN to see only incoming packets on the
interface. Set to BPF_D_INOUT to see packets originating locally and
remotely on the interface. Set to BPF_D_OUT to see only outgoing
packets on the interface. This setting is initialized to BPF_D_INOUT
by default. BIOCGSEESENT and BIOCSSEESENT are obsoleted by these but
kept for backward compatibility.
- BIOCFEEDBACK sets packet feedback mode. This allows injected packets
to be fed back as input to the interface when output via the interface is
successful. When BPF_D_INOUT direction is set, injected outgoing packet
is not returned by BPF to avoid duplication. This flag is initialized to
zero by default.
Note that libpcap has been modified to support BPF_D_OUT direction for
pcap_setdirection(3) and PCAP_D_OUT direction is functional now.
Reviewed by: rwatson
pointer to a zeroed, statically allocated bpf_if structure. This way the
LIST_EMPTY() macro will always return true. This allows us to remove the
additional unconditional memory reference for each packet in the fast path.
Discussed with: sam
resulting in some build failures. Instead, to fix the problem of bpf not
being present, check the pointer before dereferencing it.
This is a temporary bandaid until we can decide on how we want to handle
the bpf code not being present. This will be fixed shortly.
(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
enhance the security of bpf(4) by further relinquishing the privilege of
the bpf(4) consumer (assuming the ioctl commands are being implemented).
Once BIOCLOCK is executed, the device becomes locked which prevents the
execution of ioctl(2) commands which can change the underly parameters of the
bpf(4) device. An example might be the setting of bpf(4) filter programs or
attaching to different network interfaces.
BIOCSETWF can be used to set write filters for outgoing packets. Currently if
a bpf(4) consumer is compromised, the bpf(4) descriptor can essentially be used
as a raw socket, regardless of consumer's UID. Write filters give users the
ability to constrain which packets can be sent through the bpf(4) descriptor.
These features are currently implemented by a couple programs which came from
OpenBSD, such as the new dhclient and pflogd.
-Modify bpf_setf(9) to accept a "cmd" parameter. This will be used to specify
whether a read or write filter is to be set.
-Add a bpf(4) filter program as a parameter to bpf_movein(9) as we will run the
filter program on the mbuf data once we move the packet in from user-space.
-Rather than execute two uiomove operations, (one for the link header and the
other for the packet data), execute one and manually copy the linker header
into the sockaddr structure via bcopy.
-Restructure bpf_setf to compensate for write filters, as well as read.
-Adjust bpf(4) stats structures to include a bd_locked member.
It should be noted that the FreeBSD and OpenBSD implementations differ a bit in
the sense that we unconditionally enforce the lock, where OpenBSD enforces it
only if the calling credential is not root.
Idea from: OpenBSD
Reviewed by: mlaier
pf/pflog/pfsync as modules. Do not list them in NOTES or modules/Makefile
(i.e. do not connect it to any (automatic) builds - yet).
Approved by: bms(mentor)
a new bpf_mtap2 routine that does the right thing for an mbuf
and a variable-length chunk of data that should be prepended.
o while we're sweeping the drivers, use u_int32_t uniformly when
when prepending the address family (several places were assuming
sizeof(int) was 4)
o return M_ASSERTVALID to BPF_MTAP* now that all stack-allocated
mbufs have been eliminated; this may better be moved to the bpf
routines
Reviewed by: arch@ and several others
mpf are allocated on the stack, which causes this check to falsely trigger.
A new check which takes on-stack mbufs into account will be reintroduced
after 5.2 is out the door.
Approved by: re (watson)
Requested by: many
is non-free. (More checks can/should be added in the future.)
Use M_ASSERTVALID in BPF_MTAP so that we catch when freed mbufs are
passed in, even if no bpf listeners are active.
Inspired by a bug in if_dc caught by Kenjiro Cho.
and set the link type for use by libpcap and tcpdump
o move mtx unlock in bpfdetach up; it doesn't need to be held so long
o change printf in bpf_detach to distinguish it from the same one in bpfsetdlt
Note there are locking issues here related to ioctl processing; they
have not been addressed here.
Submitted by: Guy Harris <guy@alum.mit.edu>
Obtained from: NetBSD (w/ locking modifications)
o introduce BPF_TAP and BPF_MTAP macros to hide implementation details and
ease code portability
o use m_getcl where appropriate
Reviewed by: many
Approved by: re
Obtained from: NetBSD (multiple link type support)
possible for a panic to occur if BPF is in use on the interface at the
time of the call to if_detach. This happens because BPF maintains pointers
to the struct ifnet describing the interface, which is freed by if_detach.
To correct this problem, a new call, bpfdetach, is introduced. bpfdetach
locates BPF descriptor references to the interface, and NULLs them. Other
BPF code is modified so that discovery of a NULL interface results in
ENXIO (already implemented for some calls). Processes blocked on a BPF
call will also be woken up so that they can receive ENXIO.
Interface drivers that invoke bpfattach and if_detach must be modified to
also call bpfattach(ifp) before calling if_detach(ifp). This is relevant
for buses that support hot removal, such as pccard and usb. Patches to
all effected devices will not be committed, only to if_wi.c, due to
testing limitations. To reproduce the crash, load up tcpdump on you
favorite pccard ethernet card, and then eject the card. As some pccard
drivers do not invoke if_detach(ifp), this bug will not manifest itself
for those drivers.
Reviewed by: wes
not the current BPF device should report locally generated packets or not.
This allows sniffing applications to see only packets that are not generated
locally, which can be useful for debugging bridging problems, or other
situations where MAC addresses are not sufficient to identify locally
sourced packets. Default to true for this flag, so as to provide existing
behavior by default.
Introduce two new ioctls, BIOCGSEESENT and BIOCSSEESENT, which may be used
to manipulate this flag from userland, given appropriate privilege.
Modify bpf.4 to document these two new ioctl arguments.
Reviewed by: asmodai
