o push much of the i386 and amd64 MD interrupt handling code
(intr_machdep.c::intr_execute_handlers()) into MI code
(kern_intr.c::ithread_loop())
o move filter handling to kern_intr.c::intr_filter_loop()
o factor out the code necessary to mask and ack an interrupt event
(intr_machdep.c::intr_eoi_src() and intr_machdep.c::intr_disab_eoi_src()),
and make them part of 'struct intr_event', passing them as arguments to
kern_intr.c::intr_event_create().
o spawn a private ithread per handler (struct intr_handler::ih_thread)
with filter and ithread functions.
Approved by: re (implicit?)
and change it to a void function.
We use a compressed structure for TCPS_TIME_WAIT to save memory. Any late
late segments arriving for such a connection is handled directly in the TW
code.
and show up with different names: first try to open provider using
remembered name and compare its ident, if equal, this is our provider,
if not equal or there is no provider with such name, find provider with
remembered ident and don't care about the name.
- Locks were not being unlocked when an invalid size chunk is
sent in.
- When a notification comes in, we cannot use it to look up
the fragment interleave stream information since its not
on a stream.
Seems to work on RELENG_4 through -current and also on sparc64
now. There may still be some issues with the auto attach/detach
code to sort out.
MFC after: 3 days
VM_PHYSSEG_SPARSE depending on whether the physical address space is
densely or sparsely populated with memory. The effect of this
definition is to determine which of two implementations of
vm_page_array and PHYS_TO_VM_PAGE() is used. The legacy
implementation is obtained by defining VM_PHYSSEG_DENSE, and a new
implementation that trades off time for space is obtained by defining
VM_PHYSSEG_SPARSE. For now, all architectures except for ia64 and
sparc64 define VM_PHYSSEG_DENSE. Defining VM_PHYSSEG_SPARSE on ia64
allows the entirety of my Itanium 2's memory to be used. Previously,
only the first 1 GB could be used. Defining VM_PHYSSEG_SPARSE on
sparc64 allows USIIIi-based systems to boot without crashing.
This change is a combination of Nathan Whitehorn's patch and my own
work in perforce.
Discussed with: kmacy, marius, Nathan Whitehorn
PR: 112194
DIOCGFLUSH - Flush write cache (sends BIO_FLUSH).
DIOCGDELETE - Delete data (mark as unused) (sends BIO_DELETE).
DIOCGIDENT - Get provider's uniqe and fixed identifier (asks for
GEOM::ident attribute).
First two are self-explanatory, but the last one might not be. Here are
properties of provider's ident:
- ident value is preserved between reboots,
- provider can be detached/attached and ident is preserved,
- provider's name can change - ident can't,
- ident value should not be based on on-disk metadata; in other words
copying whole data from one disk to another should not yield the same
ident for the other disk,
- there could be more than one provider with the same ident, but only if
they point at exactly the same physical storage, this is the case for
multipathing for example,
- GEOM classes that consumes single providers and provide single providers,
like geli, gbde, should just attach class name to the ident of the
underlying provider,
- ident is an ASCII string (is printable),
- ident is optional and applications can't relay on its presence.
The main purpose for this is that application and remember provider's ident
and once it tries to open provider by its name again, it may compare idents
to be sure this is the right provider. If it is not (idents don't match),
then it can open provider by its ident.
OK'ed by: phk
- Make wlan_amrr depend on wlan, so that it can find various symbols in
wlan module if wlan is not compiled into kernel.
Approved by: sam (mentor)
Tested by: kevlo
- http://www.intel.com/design/chipsets/specupdt/245051.htm
AC97 Soft Audio and Soft Modem Master Abort Errata
Issue:
Use of either soft audio or soft modem on an Intel® 82443MX PCISet
based platform running a 100 MHz Processor System Bus and an AC97 codec
may result in failures. The system continues to function normally while
the AC97 hardware may not resume and may require a cold-boot to
recover. As a result of the failure, the Master Abort Status bit will
be set in the audio or modem function PCI header space.
Workaround:
Force uncacheable DMA on both BDL and pcm buffers.
Tested by: Emil Holmstr|m <emil@linux.se>
- Remove explicit call to pmap_change_attr(), since we now have proper
and functional definition of BUS_DMA_NOCACHE.
- Enable PCI(e) bus snooping for non i386/amd64 as an alternative for
uncacheable DMA.
- Codecs changes:
* Analag Device -> Analog Devices, AD1988.
* New codec: VIA VT1708 and VT1709, Realtek ALC262, ALC861-VD and
ALC885.
* Various fixups for Conexant Waikiki, fix recording (read: microphone)
on various Analog Devices codecs due to vendor BIOS mess, various
quirks for several ASUS laptops/boards.
- Fix connection list handling, closely following the specification to
handle range of nids.
- Basic Jack sense polling infrastructure for possible hardwares with
broken unsolicited response interrupt.
Ideas/Submitted/Tested by: Andriy Gapon <avg@icyb.net.ua>,
#freebsd-azalia, many.
state tcp_debug, tcp_debx. Acquire and drop as required in tcp_trace().
Move to ANSI C function header, correct prototype types so that short TCP
state is no longer promoted to int unnecessarily.
Add comments.
MFC after: 3 weeks
Updated copyright date to 2007.
Tested with BCM5706 A3.
Added ID for BCM5708 B2.
Removed unused driver version string.
Modified BCE_PRINTF macro to automatically fill-in the sc pointer.
Fixed a kernel panic when the driver was loaded as a module from the
command-line because the MII bus pointer was null (i.e. the MII bus
hadn't been enumerated yet).
Added fix proposed by Vladimir Ivanov <wawa@yandex-team.ru> to prevent
driver state corruption when releasing the lock during the ISR in
bce_rx_intr() to send packets up the stack.
Added new TX chain and register read sysctl interfaces for debugging.
Cleaned up formatting for various other debug routines.
Added a new statistic maintained by firmware which tracks the number
of received packets dropped because no receive buffers are available.
correct network drivers with respect to busmaster DMA, go over it
with at duster to make other aspects of it a role model:
Eliminate the pci specific softc, it serves no rational purpose.
Use convenience resource allocation/deallocation functions to save
code and errorhandling.
Switch from bus_space_{read|write}_%u() to bus_{read|write}_%u()
functions and forget about tags and handles, the resource will know
about those, should they be needed. This also eliminates a number
of inconsistently named local variables.
it was full and a collision occured, then we would leave
a inp locked. Also fixes a missing inp unlock if IPSEC was
on and it failed during the attach. Bug found by Weongyo Jeong.
as UF_OPENING. Disable closing of that entries. This should fix the crashes
caused by devfs_open() (and fifo_open()) dereferencing struct file * by
index, while the filedescriptor is closed by parallel thread.
Idea by: tegge
Reviewed by: tegge (previous version of patch)
Tested by: Peter Holm
Approved by: re (kensmith)
MFC after: 3 weeks
in comments for .c and .h files respectively. Jack may want to clean up
style or other aspects once he's up and about again, but this gets the
kernel compiling.
shared code infrastructure that is family specific and
modular. There is also support for our latest gigabit
nic, the 82575 that is MSI/X and multiqueue capable.
The new shared code changes some interfaces to the core
code but testing at Intel has been going on for months,
it is fairly stable.
I have attempted to be careful in retaining any fixes that
CURRENT had and we did not, I apologize in advance if any
thing gets clobbered, I'm sure I'll hear about it :)
Approved by pdeuskar
on each socket buffer with the socket buffer's mutex. This sleep lock is
used to serialize I/O on sockets in order to prevent I/O interlacing.
This change replaces the custom sleep lock with an sx(9) lock, which
results in marginally better performance, better handling of contention
during simultaneous socket I/O across multiple threads, and a cleaner
separation between the different layers of locking in socket buffers.
Specifically, the socket buffer mutex is now solely responsible for
serializing simultaneous operation on the socket buffer data structure,
and not for I/O serialization.
While here, fix two historic bugs:
(1) a bug allowing I/O to be occasionally interlaced during long I/O
operations (discovere by Isilon).
(2) a bug in which failed non-blocking acquisition of the socket buffer
I/O serialization lock might be ignored (discovered by sam).
SCTP portion of this patch submitted by rrs.
- Simplify the amount of work that has be done for each architecture by
pushing more of the truly MI code down into the PCI bus driver.
- Don't bind MSI-X indicies to IRQs so that we can allow a driver to map
multiple MSI-X messages into a single IRQ when handling a message
shortage.
The changes include:
- Add a new pcib_if method: PCIB_MAP_MSI() which is called by the PCI bus
to calculate the address and data values for a given MSI/MSI-X IRQ.
The x86 nexus drivers map this into a call to a new 'msi_map()' function
in msi.c that does the mapping.
- Retire the pcib_if method PCIB_REMAP_MSIX() and remove the 'index'
parameter from PCIB_ALLOC_MSIX(). MD code no longer has any knowledge
of the MSI-X index for a given MSI-X IRQ.
- The PCI bus driver now stores more MSI-X state in a child's ivars.
Specifically, it now stores an array of IRQs (called "message vectors" in
the code) that have associated address and data values, and a small
virtual version of the MSI-X table that specifies the message vector
that a given MSI-X table entry uses. Sparse mappings are permitted in
the virtual table.
- The PCI bus driver now configures the MSI and MSI-X address/data
registers directly via custom bus_setup_intr() and bus_teardown_intr()
methods. pci_setup_intr() invokes PCIB_MAP_MSI() to determine the
address and data values for a given message as needed. The MD code
no longer has to call back down into the PCI bus code to set these
values from the nexus' bus_setup_intr() handler.
- The PCI bus code provides a callout (pci_remap_msi_irq()) that the MD
code can call to force the PCI bus to re-invoke PCIB_MAP_MSI() to get
new values of the address and data fields for a given IRQ. The x86
MSI code uses this when an MSI IRQ is moved to a different CPU, requiring
a new value of the 'address' field.
- The x86 MSI psuedo-driver loses a lot of code, and in fact the separate
MSI/MSI-X pseudo-PICs are collapsed down into a single MSI PIC driver
since the only remaining diff between the two is a substring in a
bootverbose printf.
- The PCI bus driver will now restore MSI-X state (including programming
entries in the MSI-X table) on device resume.
- The interface for pci_remap_msix() has changed. Instead of accepting
indices for the allocated vectors, it accepts a mini-virtual table
(with a new length parameter). This table is an array of u_ints, where
each value specifies which allocated message vector to use for the
corresponding MSI-X message. A vector of 0 forces a message to not
have an associated IRQ. The device may choose to only use some of the
IRQs assigned, in which case the unused IRQs must be at the "end" and
will be released back to the system. This allows a driver to use the
same remap table for different shortage values. For example, if a driver
wants 4 messages, it can use the same remap table (which only uses the
first two messages) for the cases when it only gets 2 or 3 messages and
in the latter case the PCI bus will release the 3rd IRQ back to the
system.
MFC after: 1 month
set/clear it but would not do it. Now we will.
- Moved to latest socket api for extended sndrcv info struct.
- Moved to support all new levels of fragment interleave (0-2).
- Codenomicon security test updates - length checks and such.
- Bug in stream reset (2 actually).
- setpeerprimary could unlock a null pointer, fixed.
- Added a flag in the pcb so netstat can see if we are listening easier.
Obtained from: (some of the Listen changes from Weongyo Jeong)
pointers. A structure is more readable and less error-prone. It
also avoids problems when a function pointer doesn't have the
same width as a void pointer.
functions with CPUs they apply to only, otherwise default to the
plain C functions. This is modeled in a way so that f.e. a Cheetah
version of these functions can be inserted easily.
Not because I admit they are technically wrong and not because of bug
reports (I receive nothing). But because I surprisingly meets so
strong opposition and resistance so lost any desire to continue that.
Anyone who interested in POSIX can dig out what changes and how
through cvs diffs.
the UPA_IMR2 resource is also shared with/a subset of the Schizo PCI
bus B CSR bank. I'm not entirely sure how this previously managed to
escape testing...
consistent with the naming of other structure field members, and
reducing improper grep matches. Clean up and comment structure
fields in structure definition.
sc->mii_anegticks according to whether the respective BGE chip
supports Fast Ethernet only or also Gigabit Ethernet.
- At least the BGE chips I've tested with wedge when isolating them
so document this as the reason for setting MIIF_NOISOLATE and
remove the unused (and partially even #ifdef'ed out) isolation
related code. Add code that panics if we encounter a non-zero MII
instance as generally there's no way a PHY requiring MIIF_NOISOLATE
can be handled gracefully in a multi-PHY configuration (it's ok for
the internal PHY of single-PHY-only-NIC to not support isolation
though).
- Additionally set MIIF_NOLOOP as loopback doesn't seem to work
either and remove the #ifdef'ed out code for adding respective
media. The MIIF_NOLOOP flag currently triggers nothing but
hopefully will be respected by mii_phy_setmedia() later on.
Reviewed by: jkim, yongari
MFC after: 1 month
Blade 2500, Fire V210 and probably some other sparc64 machines.
These chips are typically not fitted with an EEPROM which means
that we have to obtain the MAC address via OFW and that some chip
tests will just always fail.
These changes are based on the respective code found in OpenBSD
with some additional info obtained from OpenSolaris and some style
suggestions by jkim@. They also have the desired side-effect of
respecting the 'local-mac-address?' system configuration variable
for the affected BGEs.
- In bge_attach() factor out calling bge_release_resources() before
going to the fail label into the fail label as well as replace a
magic 6 with ETHER_ADDR_LEN.
Reviewed by: yongari (before style changes), jkim
- Wake up DMA engine after adding a new receive buffer.
- Skip buffers which have unknown state after error.
- More rigid error detection.
MFC after: 1 week
as some combinations of chipset, controller and target do not behave
correctly when DMA is enabled for other commands.
PR: kern/103602
MFC after: 2 weeks
were never freed, but the big ring was freed twice.
-Don't supply rx hw csums for frames which are padded beyond the
length specified in the ip header. If the padding is non-zero,
the hw csum will be incorrect for such frames.
Sponsored by: Myricom
non-mapped data as possible at once and not page-by-page. Which this change we
combain I/Os, but also saves many VM_OBJECT_UNLOCK()/VM_OBJECT_LOCK()
operations.
Simple 'fsx -l 33554432 -o 524288 -N 10000 /tank/fsx' test shows ~23%
performance increase.
This workaround the problem in Parallels/VMWare where the emulated drivers are
slower, especially with ATA_FLUSHCACHE. The problem appears much more
frequently with ZFS which use it a lot more.
Approved: sos, pjd
- vm_page_undirty() is enough (instead of vm_page_set_validclean()), but it has
to be called before we write the data in case someone makes page dirty after
our write, but before our vm_page_undirty() call.
- Always dmu_write, not matter if uiomove() succeeded, because it could
partially be ok and we would lose some changes.
All good ideas from: ups
In dounmount(), before or while vn_lock(coveredvp) is called, coveredvp
vnode may be VI_DOOMED due to one of the following:
- other thread finished unmount and vput()ed it, and vnode was chosen
for recycling, while vn_lock() slept;
- forced unmount of the coveredvp->v_mount fs.
In the first case, next check for changed v_mountedhere or mnt_gen counter
would be successfull. In the second case, the unmount shall be allowed.
Submitted by: sobomax
MFC after: 2 weeks
- Fix for a bug where a close would not wait for all (directio)
dirty buffers to drain. The nfsnode was not marked NMODIFIED
when there were directio dirtied buffers pending, causing this.
- No reason to vhold/vrele the vp when enqueueing DirectIO requests
for the nfsiods. The vnode can't really go way since the close
has to wait for these requests to drain.
MFC after: 1 week
Submitted by: mohans
specific request and thus should first try to be allocated from the
sys_resource pool. This avoids using the sys_resource pool for wildcard
requests that have bounded ranges coming from cbb(4) and Host-PCI pcib(4)
drivers.
Tested by: Andrea Bittau <a.bittau of cs.ucl.ac.uk fame>
Sleuthing by: Andrea Bittau as well
that the MSI mapping window is fixed at 0xfee00000 and the capability
does not include two more dwords used to program the address. Supporting
this mostly results in quieting spurious warnings during boot about
non-default MSI mapping windows.
- HT 2.00b also added a new HT capability type, so support that in pciconf.
MFC after: 3 days
Tested by: jmg
It seems that valid pause frames(Tx flow control) cause GMAC to hang
such that it resulted in watchdog timeout. As a work around don't
flush Rx MAC FIFO if we've received pause frames.
Tested by: Harald Schmalzbauer (h DOT schmalzbauer AT omnisec DOT de)
Under certain circumtances, if TSO is active, Yukon II generates
corrupted IP packets. All corrupted IP packets I noticed were the the
last segmented packet in a TSO request. The corrupted packet resulted
in retransmission of the damaged packet which in turn decreased network
performance dramatically.
Unfortunately it seems that there is no way to workaround this bug
as TSO is completely handled in hardware. Disable TSO until we find a
working workaround or a new silicon revision that doesn't have this
hardware bug.
fault. The previous method zero'd out the page tables, invalidated the
TLB, and then entered a spin loop. The idea was that the instruction after
the TLB invalidate would result in a page fault and the page fault and
subsequent double fault wouldn't be able to determine the physical page
for their fault handlers' first instruction. This stopped working when
PGE (PG_G PTE/PDE bit) support was added as a TLB invalidate via %cr3
reload doesn't clear TLB entries with PG_G set. Thus, the CPU was still
able to map the virtual address for the spin loop and happily performed
its infinite loop.
The triple fault now uses a much more deterministic sledge-hammer approach
to generate a triple fault. First, the IDT descriptor is set to point to
an empty IDT, so any interrupts (including a double fault) will instantly
fault. Second, we trigger a int 3 breakpoint to force an interrupt and
kick off a triple fault.
MFC after: 3 days
in all other file system on FreeBSD (instead from inactive() method).
A nice side-effect of this change, except that it speedups file system
when mmaped file are often open/closed, is that it makes FreeBSD's
namecache work:)
This fixes slow operations on mmaped files, because without this fix,
pages were written to disk multiple times.
If one is looking for even greater speed up for such operation, he should
disable ZIL (by setting vfs.zfs.zil_disable to 1 in /boot/loader.conf).
Disabling ZIL makes fsx run ~9 times faster.
supports software encrypt/decrypt.
The nuked code itself is quite problematic, as pointed out by sam@ ---
wk->wk_keyix should be replaced by the loop count.
Tested with WEP/TKIP/CCMP/no-protection.
Approved by: sam@ (mentor)
Noticed by: Hans Petter Selasky <hselasky@c2i.net>
o Fix linewrap issues.
o Fix two typos (s/Recomended/Recommended/ and s/tunning/tuning/)
o Remove a couple of extra instances of the word "of".
o Update names of kmem_size variables.
Approved by: pjd
where similar data structures exist to support devfs and the MAC
Framework, but are named differently.
Obtained from: TrustedBSD Project
Sponsored by: SPARTA, Inc.
by Philippe Biondi and Arnaud Ebalard. This is a temporary fix
until more discussion can be had on the exact risks involved in
allowing source routing in IPv6
Submitted by: itojun
Reviewed by: jinmei
MFC after: 1 day
- Move FreeBSD-specific code to zfs_freebsd_*() functions in zfs_vnops.c
and keep original functions as similar to vendor's code as possible.
- Add various includes back, now that we have them.
macro, as za_first_integer field also contains type. This should be fixed in
ZFS itself, but this bug is not visible on Solaris, because there, type is
not stored in za_first_integer. On the other hand it will be visible on
MacOS X.
Reported by: Barry Pederson <bp@barryp.org>
variable name conventions for arguments passed into the framework --
for example, name network interfaces 'ifp', sockets 'so', mounts 'mp',
mbufs 'm', processes 'p', etc, wherever possible. Previously there
was significant variation in this regard.
Normalize copyright lists to ranges where sensible.
labels: the mount label (label of the mountpoint) and the fs label (label
of the file system). In practice, policies appear to only ever use one,
and the distinction is not helpful.
Combine mnt_mntlabel and mnt_fslabel into a single mnt_label, and
eliminate extra machinery required to maintain the additional label.
Update policies to reflect removal of extra entry points and label.
Obtained from: TrustedBSD Project
Sponsored by: SPARTA, Inc.
the introduction of priv(9) and MAC Framework entry points for privilege
checking/granting. These entry points exactly aligned with privileges and
provided no additional security context:
- mac_check_sysarch_ioperm()
- mac_check_kld_unload()
- mac_check_settime()
- mac_check_system_nfsd()
Add mpo_priv_check() implementations to Biba and LOMAC policies, which,
for each privilege, determine if they can be granted to processes
considered unprivileged by those two policies. These mostly, but not
entirely, align with the set of privileges granted in jails.
Obtained from: TrustedBSD Project
- Redistribute counter declarations to where they are used, rather than at
the file header, so it's more clear where we do (and don't) have
counters.
- Add many more counters, one per policy entry point, so that many
individual access controls and object life cycle events are tracked.
- Perform counter increments for label destruction explicitly in entry
point functions rather than in LABEL_DESTROY().
- Use LABEL_INIT() instead of SLOT_SET() directly in label init functions
to be symmetric with destruction.
- Align counter names more carefully with entry point names.
- More constant and variable name normalization.
Obtained from: TrustedBSD Project
- Add a more detailed comment describing the mac_test policy.
- Add COUNTER_DECL() and COUNTER_INC() macros to declare and manage
various test counters, reducing the verbosity of the test policy
quite a bit.
- Add LABEL_CHECK() macro to abbreviate normal validation of labels.
Unlike the previous check macros, this checks for a NULL label and
doesn't test NULL labels. This means that optionally passed labels
will now be handled automatically, although in the case of optional
credentials, NULL-checks are still required.
- Add LABEL_DESTROY() macro to abbreviate the handling of label
validation and tear-down.
- Add LABEL_NOTFREE() macro to abbreviate check for non-free labels.
- Normalize the names of counters, magic values.
- Remove unused policy "enabled" flag.
Obtained from: TrustedBSD Project
set/clear it but would not do it. Now we will.
- Moved to latest socket api for extended sndrcv info struct.
- Moved to support all new levels of fragment interleave.
calls. Add MAC Framework entry points and MAC policy entry points for
audit(), auditctl(), auditon(), setaudit(), aud setauid().
MAC Framework entry points are only added for audit system calls where
additional argument context may be useful for policy decision-making; other
audit system calls without arguments may be controlled via the priv(9)
entry points.
Update various policy modules to implement audit-related checks, and in
some cases, other missing system-related checks.
Obtained from: TrustedBSD Project
Sponsored by: SPARTA, Inc.
- Replace PRIV_NFSD with PRIV_NFS_DAEMON, add PRIV_NFS_LOCKD.
- Use PRIV_NFS_DAEMON in the NFS server.
- In the NFS client, move the privilege check from nfslockdans(), which
occurs every time a write is performed on /dev/nfslock, and instead do it
in nfslock_open() just once. This allows us to avoid checking the saved
uid for root, and just use the effective on open. Use PRIV_NFS_LOCKD.
@118370 Correct typo.
@118371 Integrate changes from vendor.
@118491 Show backtrace on unexpected code paths.
@118494 Integrate changes from vendor.
@118504 Fix sendfile(2). I had two ways of fixing it:
1. Fixing sendfile(2) itself to use VOP_GETPAGES() instead of
hacking around with vn_rdwr(UIO_NOCOPY), which was suggested
by ups.
2. Modify ZFS behaviour to handle this special case.
Although 1 is more correct, I've choosen 2, because hack from 1
have a side-effect of beeing faster - it reads ahead MAXBSIZE
bytes instead of reading page by page. This is not easy to implement
with VOP_GETPAGES(), at least not for me in this very moment.
Reported by: Andrey V. Elsukov <bu7cher@yandex.ru>
@118525 Reorganize the code to reduce diff.
@118526 This code path is expected. It is simply when file is opened with
O_FSYNC flag.
Reported by: kris
Reported by: Michal Suszko <dry@dry.pl>
vm.kmem_size_min. Useful when using ZFS to make sure that vm.kmem size will
be at least 256mb (for example) without forcing a particular value via vm.kmem_size.
Approved by: njl (mentor)
Reviewed by: alc
from the incoming SYN handling section of tcp_input().
Enforcement of the accept queue limits is done by sonewconn() after the
3WHS is completed. It is not necessary to have an earlier check before a
connection request enters the SYN cache awaiting the full handshake. It
rather limits the effectiveness of the syncache by preventing legit and
illegit connections from entering it and having them shaken out before we
hit the real limit which may have vanished by then.
Change return value of syncache_add() to void. No status communication
is required.
when the ACK is invalid and doesn't belong to any registered connection,
either in syncache or through SYN cookies. True but a NULL struct socket
is returned when the 3WHS completed but the socket could not be created
due to insufficient resources or limits reached.
For both cases an RST is sent back in tcp_input().
A logic error leading to a panic is fixed where syncache_expand() would
free the mbuf on socket allocation failure but tcp_input() later supplies
it to tcp_dropwithreset() to issue a RST to the peer.
Reported by: kris (the panic)
