Commit Graph

183 Commits

Author SHA1 Message Date
Kristof Provost
0df377cbb8 pf: Add missing byte-order swap to pf_match_addr_range
Without this, rules using address ranges (e.g. "10.1.1.1 - 10.1.1.5") did not
match addresses correctly on little-endian systems.

PR:		211796
Obtained from:	OpenBSD (sthen)
MFC after:	3 days
2016-08-15 12:13:14 +00:00
Kristof Provost
aa7cac58c6 pf: Map hook returns onto the correct error values
pf returns PF_PASS, PF_DROP, ... in the netpfil hooks, but the hook callers
expect to get E<foo> error codes.
Map the returns values. A pass is 0 (everything is OK), anything else means
pf ate the packet, so return EACCES, which tells the stack not to emit an ICMP
error message.

PR:	207598
2016-07-09 12:17:01 +00:00
Bjoern A. Zeeb
a8fc1b786d The void isn't void.
Unbreak sparc64 and powerpc builds.

Approved by:	re (gjb)
Sponsored by:	The FreeBSD Foundation
MFC after:	12 days
2016-06-24 11:53:12 +00:00
Bjoern A. Zeeb
66c00e9efb Proerply virtualize pfsync for bringup after pf is initialized and
teardown of VNETs once pf(4) has been shut down.
Properly split resources into VNET_SYS(UN)INITs and one time module
loading.
While here cover the INET parts in the uninit callpath with proper
#ifdefs.

Approved by:	re (gjb)
Obtained from:  projects/vnet
MFC after:      2 weeks
Sponsored by:   The FreeBSD Foundation
2016-06-23 22:31:44 +00:00
Bjoern A. Zeeb
7d7751a071 Make sure pflog is attached after pf is initializaed so we can
borrow pf's lock, and also make sure pflog goes after pf is gone
in order to avoid callouts in VNETs to an already freed instance.

Reported by:    Ivan Klymenko, Johan Hendriks  on current@ today
Obtained from:  projects/vnet
Sponsored by:   The FreeBSD Foundation
MFC after:      13 days
Approved by:	re (gjb)
2016-06-23 22:31:10 +00:00
Bjoern A. Zeeb
a8e8c57443 PFSTATE_NOSYNC goes onto state_flags, not sync_state;
this prevents: panic: pfsync_delete_state: unexpected sync state 8

Reviewed by:		kp
Approved by:		re (gjb)
MFC after:		2 weeks
Sponsored by:		The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D6942
2016-06-23 21:42:43 +00:00
Bjoern A. Zeeb
a0429b5459 Update pf(4) and pflog(4) to survive basic VNET testing, which includes
proper virtualisation, teardown, avoiding use-after-free, race conditions,
no longer creating a thread per VNET (which could easily be a couple of
thousand threads), gracefully ignoring global events (e.g., eventhandlers)
on teardown, clearing various globally cached pointers and checking
them before use.

Reviewed by:		kp
Approved by:		re (gjb)
Sponsored by:		The FreeBSD Foundation
MFC after:		2 weeks
Differential Revision:	https://reviews.freebsd.org/D6924
2016-06-23 21:34:38 +00:00
Bjoern A. Zeeb
8147948e19 Import a fix for and old security issue (CVE-2010-3830) in pf which
was not relevant to FreeBSD as only root could open /dev/pf by default.
With VIMAGE this is will longer be the case.  As pf(4) starts to
be supported with VNETs 3rd party users may open /dev/pf inside the
virtual jail instance; thus we need to address this issue after all.
While OpenBSD largely rewrote code parts for the fix [1], and it's
unclear what Apple [3] did, import the minimal fix from NetBSD [2].

[1] http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/sys/net/pf_ioctl.c.diff?r1=1.235&r2=1.236
[2] http://mail-index.netbsd.org/source-changes/2011/01/19/msg017518.html
[3] https://support.apple.com/en-gb/HT202154

Obtained from:		http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/dist/pf/net/pf_ioctl.c.diff?r1=1.42&r2=1.43&only_with_tag=MAIN
MFC After:		2 weeks
Approved by:		re (gjb)
Sponsored by:		The FreeBSD Foundation
Security:		CVE-2010-3830
2016-06-23 05:41:46 +00:00
Bjoern A. Zeeb
89856f7e2d Get closer to a VIMAGE network stack teardown from top to bottom rather
than removing the network interfaces first. This change is rather larger
and convoluted as the ordering requirements cannot be separated.

Move the pfil(9) framework to SI_SUB_PROTO_PFIL, move Firewalls and
related modules to their own SI_SUB_PROTO_FIREWALL.
Move initialization of "physical" interfaces to SI_SUB_DRIVERS,
move virtual (cloned) interfaces to SI_SUB_PSEUDO.
Move Multicast to SI_SUB_PROTO_MC.

Re-work parts of multicast initialisation and teardown, not taking the
huge amount of memory into account if used as a module yet.

For interface teardown we try to do as many of them as we can on
SI_SUB_INIT_IF, but for some this makes no sense, e.g., when tunnelling
over a higher layer protocol such as IP. In that case the interface
has to go along (or before) the higher layer protocol is shutdown.

Kernel hhooks need to go last on teardown as they may be used at various
higher layers and we cannot remove them before we cleaned up the higher
layers.

For interface teardown there are multiple paths:
(a) a cloned interface is destroyed (inside a VIMAGE or in the base system),
(b) any interface is moved from a virtual network stack to a different
network stack ("vmove"), or (c) a virtual network stack is being shut down.
All code paths go through if_detach_internal() where we, depending on the
vmove flag or the vnet state, make a decision on how much to shut down;
in case we are destroying a VNET the individual protocol layers will
cleanup their own parts thus we cannot do so again for each interface as
we end up with, e.g., double-frees, destroying locks twice or acquiring
already destroyed locks.
When calling into protocol cleanups we equally have to tell them
whether they need to detach upper layer protocols ("ulp") or not
(e.g., in6_ifdetach()).

Provide or enahnce helper functions to do proper cleanup at a protocol
rather than at an interface level.

Approved by:		re (hrs)
Obtained from:		projects/vnet
Reviewed by:		gnn, jhb
Sponsored by:		The FreeBSD Foundation
MFC after:		2 weeks
Differential Revision:	https://reviews.freebsd.org/D6747
2016-06-21 13:48:49 +00:00
Kristof Provost
3e248e0fb4 pf: Filter on and set vlan PCP values
Adopt the OpenBSD syntax for setting and filtering on VLAN PCP values. This
introduces two new keywords: 'set prio' to set the PCP value, and 'prio' to
filter on it.

Reviewed by:    allanjude, araujo
Approved by:	re (gjb)
Obtained from:  OpenBSD (mostly)
Differential Revision:  https://reviews.freebsd.org/D6786
2016-06-17 18:21:55 +00:00
Kristof Provost
b599e8dc59 pf: Fix more ICMP mistranslation
In the default case fix the substitution of the destination address.

PR:		201519
Submitted by:	Max <maximos@als.nnov.ru>
MFC after:	1 week
2016-05-23 13:59:48 +00:00
Kristof Provost
c0c82715b8 pf: Fix ICMP translation
Fix ICMP source address rewriting in rdr scenarios.

PR:		201519
Submitted by:	Max <maximos@als.nnov.ru>
MFC after:	1 week
2016-05-23 12:41:29 +00:00
Kristof Provost
d9f4fce5a7 pf: Fix fragment timeout
We were inconsistent about the use of time_second vs. time_uptime.
Always use time_uptime so the value can be meaningfully compared.

Submitted by:	"Max" <maximos@als.nnov.ru>
MFC after:	4 days
2016-05-20 15:41:05 +00:00
Pedro F. Giffuni
a4641f4eaa sys/net*: minor spelling fixes.
No functional change.
2016-05-03 18:05:43 +00:00
Kristof Provost
0d8c93313e pf: Improve forwarding detection
When we guess the nature of the outbound packet (output vs. forwarding) we need
to take bridges into account. When bridging the input interface does not match
the output interface, but we're not forwarding. Similarly, it's possible for the
interface to actually be the bridge interface itself (and not a member interface).

PR:		202351
MFC after:	2 weeks
2016-03-16 06:42:15 +00:00
Kristof Provost
14b5e85b18 pf: Fix possible out-of-bounds write
In the DIOCRSETADDRS ioctl() handler we allocate a table for struct pfr_addrs,
which is processed in pfr_set_addrs(). At the users request we also provide
feedback on the deleted addresses, by storing them after the new list
('bcopy(&ad, addr + size + i, sizeof(ad));' in pfr_set_addrs()).

This means we write outside the bounds of the buffer we've just allocated.
We need to look at pfrio_size2 instead (i.e. the size the user reserved for our
feedback). That'd allow a malicious user to specify a smaller pfrio_size2 than
pfrio_size though, in which case we'd still read outside of the allocated
buffer. Instead we allocate the largest of the two values.

Reported By:	Paul J Murphy <paul@inetstat.net>
PR:		207463
MFC after:	5 days
Differential Revision:	https://reviews.freebsd.org/D5426
2016-02-25 07:33:59 +00:00
Kristof Provost
c90369f880 in pf_print_state_parts, do not use skw->proto to print the protocol but our
local copy proto that we very carefully set beforehands. skw being NULL is
perfectly valid there.

Obtained from:	OpenBSD (henning)
2016-02-20 12:53:53 +00:00
Alexander V. Chernikov
61eee0e202 MFP r287070,r287073: split radix implementation and route table structure.
There are number of radix consumers in kernel land (pf,ipfw,nfs,route)
  with different requirements. In fact, first 3 don't have _any_ requirements
  and first 2 does not use radix locking. On the other hand, routing
  structure do have these requirements (rnh_gen, multipath, custom
  to-be-added control plane functions, different locking).
Additionally, radix should not known anything about its consumers internals.

So, radix code now uses tiny 'struct radix_head' structure along with
  internal 'struct radix_mask_head' instead of 'struct radix_node_head'.
  Existing consumers still uses the same 'struct radix_node_head' with
  slight modifications: they need to pass pointer to (embedded)
  'struct radix_head' to all radix callbacks.

Routing code now uses new 'struct rib_head' with different locking macro:
  RADIX_NODE_HEAD prefix was renamed to RIB_ (which stands for routing
  information base).

New net/route_var.h header was added to hold routing subsystem internal
  data. 'struct rib_head' was placed there. 'struct rtentry' will also
  be moved there soon.
2016-01-25 06:33:15 +00:00
Alexander V. Chernikov
ea8d14925c Remove sys/eventhandler.h from net/route.h
Reviewed by:	ae
2016-01-09 09:34:39 +00:00
Alexander V. Chernikov
460a5b502f Convert pf(4) to the new routing API.
Differential Revision:	https://reviews.freebsd.org/D4763
2016-01-07 10:20:03 +00:00
Alexander V. Chernikov
637670e77e Bring back the ability of passing cached route via nd6_output_ifp(). 2015-11-15 16:02:22 +00:00
Randall Stewart
7c4676ddee This fixes several places where callout_stops return is examined. The
new return codes of -1 were mistakenly being considered "true". Callout_stop
now returns -1 to indicate the callout had either already completed or
was not running and 0 to indicate it could not be stopped.  Also update
the manual page to make it more consistent no non-zero in the callout_stop
or callout_reset descriptions.

MFC after:	1 Month with associated callout change.
2015-11-13 22:51:35 +00:00
Kristof Provost
5a505b317a pf: Fix broken rule skip calculation
r289932 accidentally broke the rule skip calculation. The address family
argument to PF_ANEQ() is now important, and because it was set to 0 the macro
always evaluated to false.
This resulted in incorrect skip values, which in turn broke the rule
evaluations.
2015-11-07 23:51:42 +00:00
Kristof Provost
679e3c77b7 pf: Fix IPv6 checksums with route-to.
When using route-to (or reply-to) pf sends the packet directly to the output
interface. If that interface doesn't support checksum offloading the checksum
has to be calculated in software.
That was already done in the IPv4 case, but not for the IPv6 case. As a result
we'd emit packets with pseudo-header checksums (i.e. incorrect checksums).

This issue was exposed by the changes in r289316 when pf stopped performing full
checksum calculations for all packets.

Submitted by:	Luoqi Chen
MFC after:	1 week
2015-10-29 20:45:53 +00:00
Alexander V. Chernikov
78546dad4e Eliminate last rtalloc_ign() caller.
Differential Revision:	https://reviews.freebsd.org/D3927
2015-10-27 21:25:40 +00:00
Kristof Provost
c110fc49da pf: Fix TSO issues
In certain configurations (mostly but not exclusively as a VM on Xen) pf
produced packets with an invalid TCP checksum.

The problem was that pf could only handle packets with a full checksum. The
FreeBSD IP stack produces TCP packets with a pseudo-header checksum (only
addresses, length and protocol).
Certain network interfaces expect to see the pseudo-header checksum, so they
end up producing packets with invalid checksums.

To fix this stop calculating the full checksum and teach pf to only update TCP
checksums if TSO is disabled or the change affects the pseudo-header checksum.

PR:		154428, 193579, 198868
Reviewed by:	sbruno
MFC after:	1 week
Relnotes:	yes
Sponsored by:	RootBSD
Differential Revision:	https://reviews.freebsd.org/D3779
2015-10-14 16:21:41 +00:00
Alexander V. Chernikov
1fe201c322 Simplify the way of attaching IPv6 link-layer header.
Problem description:
How do we currently perform layer 2 resolution and header imposition:

For IPv4 we have the following chain:
  ip_output() -> (ether|atm|whatever)_output() -> arpresolve()

Lookup is done in proper place (link-layer output routine) and it is possible
  to provide cached lle data.

For IPv6 situation is more complex:
  ip6_output() -> nd6_output() -> nd6_output_ifp() -> (whatever)_output() ->
    nd6_storelladdr()

We have ip6_ouput() which calls nd6_output() instead of link output routine.
nd6_output() does the following:
  * checks if lle exists, creates it if needed (similar to arpresolve())
  * performes lle state transitions (similar to arpresolve())
  * calls nd6_output_ifp() which pushes packets to link output routine along
    with running SeND/MAC hooks regardless of lle state
    (e.g. works as run-hooks placeholder).

After that, iface output routine like ether_output() calls nd6_storelladdr()
  which performs lle lookup once again.

As a result, we perform lookup twice for each outgoing packet for most types
  of interfaces. We also need to maintain runtime-checked table of 'nd6-free'
  interfaces (see nd6_need_cache()).

Fix this behavior by eliminating first ND lookup. To be more specific:
  * make all nd6_output() consumers use nd6_output_ifp() instead
  * rename nd6_output[_slow]() to nd6_resolve_[slow]()
  * convert nd6_resolve() and nd6_resolve_slow() to arpresolve() semantics,
    e.g. copy L2 address to buffer instead of pushing packet towards lower
    layers
  * Make all nd6_storelladdr() users use nd6_resolve()
  * eliminate nd6_storelladdr()

The resulting callchain is the following:
  ip6_output() -> nd6_output_ifp() -> (whatever)_output() -> nd6_resolve()

Error handling:
Currently sending packet to non-existing la results in ip6_<output|forward>
  -> nd6_output() -> nd6_output _lle() which returns 0.
In new scenario packet is propagated to <ether|whatever>_output() ->
  nd6_resolve() which will return EWOULDBLOCK, and that result
  will be converted to 0.

(And EWOULDBLOCK is actually used by IB/TOE code).

Sponsored by:		Yandex LLC
Differential Revision:	https://reviews.freebsd.org/D1469
2015-09-16 14:26:28 +00:00
Kristof Provost
2f6c345adf pf: Fix misdetection of forwarding when net.link.bridge.pfil_bridge is set
If net.link.bridge.pfil_bridge is set we can end up thinking we're forwarding in
pf_test6() because the rcvif and the ifp (output interface) are different.
In that case we're bridging though, and the rcvif the the bridge member on which
the packet was received and ifp is the bridge itself.
If we'd set dir to PF_FWD we'd end up calling ip6_forward() which is incorrect.

Instead check if the rcvif is a member of the ifp bridge. (In other words, the
if_bridge is the ifp's softc). If that's the case we're not forwarding but
bridging.

PR:	202351
Reviewed by:	eri
Differential Revision:	https://reviews.freebsd.org/D3534
2015-09-01 19:04:04 +00:00
Kristof Provost
64b3b4d611 pf: Remove support for 'scrub fragment crop|drop-ovl'
The crop/drop-ovl fragment scrub modes are not very useful and likely to confuse
users into making poor choices.
It's also a fairly large amount of complex code, so just remove the support
altogether.

Users who have 'scrub fragment crop|drop-ovl' in their pf configuration will be
implicitly converted to 'scrub fragment reassemble'.

Reviewed by:	gnn, eri
Relnotes:	yes
Differential Revision:	https://reviews.freebsd.org/D3466
2015-08-27 21:27:47 +00:00
Luiz Otavio O Souza
22932fc9be Reapply r196551 which was accidentally reverted by r223637 (update to
OpenBSD pf 4.5).

Fix argument ordering to memcpy as well as the size of the copy in the
(theoretical) case that pfi_buffer_cnt should be greater than ~_max.

This fix the failure when you hit the self table size and force it to be
resized.

MFC after:	3 days
Sponsored by:	Rubicon Communications (Netgate)
2015-08-24 21:41:05 +00:00
Luiz Otavio O Souza
0a70aaf8f5 Add ALTQ(9) support for the CoDel algorithm.
CoDel is a parameterless queue discipline that handles variable bandwidth
and RTT.

It can be used as the single queue discipline on an interface or as a sub
discipline of existing queue disciplines such as PRIQ, CBQ, HFSC, FAIRQ.

Differential Revision:	https://reviews.freebsd.org/D3272
Reviewd by:	rpaulo, gnn (previous version)
Obtained from:	pfSense
Sponsored by:	Rubicon Communications (Netgate)
2015-08-21 22:02:22 +00:00
Luiz Otavio O Souza
f2fc809dcd Fix the copy of addresses passed from userland in table replace command.
The size2 is the maximum userland buffer size (used when the addresses are
copied back to userland).

Obtained from:	pfSense
MFC after:	3 days
Sponsored by:	Rubicon Communications (Netgate)
2015-08-17 23:03:54 +00:00
Mariusz Zaborski
643ef281cd Use correct src/dst ports when removing states.
Submitted by:	Milosz Kaniewski <m.kaniewski@wheelsystems.com>,
		UMEZAWA Takeshi <umezawa@iij.ad.jp> (orginal)
Reviewed by:	glebius
Approved by:	pjd (mentor)
Obtained from:	OpenBSD
MFC after:	3 days
2015-08-11 17:24:34 +00:00
Kristof Provost
48c29b118e pf: Always initialise pf_fragment.fr_flags
When we allocate the struct pf_fragment in pf_fillup_fragment() we forgot to
initialise the fr_flags field. As a result we sometimes mistakenly thought the
fragment to not be a buffered fragment. This resulted in panics because we'd end
up freeing the pf_fragment but not removing it from V_pf_fragqueue (believing it
to be part of V_pf_cachequeue).
The next time we iterated V_pf_fragqueue we'd use a freed object and panic.

While here also fix a pf_fragment use after free in pf_normalize_ip().
pf_reassemble() frees the pf_fragment, so we can't use it any more.

PR:		201879, 201932
MFC after:	5 days
2015-07-29 06:35:36 +00:00
Renato Botelho
299c819a75 Simplify logic added in r285945 as suggested by glebius
Approved by:	glebius
MFC after:	3 days
Sponsored by:	Netgate
2015-07-28 14:59:29 +00:00
Renato Botelho
b1b98a2db7 Respect pf rule log option before log dropped packets with IP options or
dangerous v6 headers

Reviewed by:	gnn, eri
Approved by:	gnn
Obtained from:	pfSense
MFC after:	3 days
Sponsored by:	Netgate
Differential Revision:	https://reviews.freebsd.org/D3222
2015-07-28 10:31:34 +00:00
Gleb Smirnoff
3e437fd2c6 Fix a typo in r280169. Of course we are interested in deleting nsn only
if we have just created it and we were the last reference.

Submitted by:	dhartmei
2015-07-28 09:36:26 +00:00
Ermal Luçi
a5b789f65a ALTQ FAIRQ discipline import from DragonFLY
Differential Revision:  https://reviews.freebsd.org/D2847
Reviewed by:    glebius, wblock(manpage)
Approved by:    gnn(mentor)
Obtained from:  pfSense
Sponsored by:   Netgate
2015-06-24 19:16:41 +00:00
Kristof Provost
06ba348d27 pf: Remove frc_direction
We don't use the direction of the fragments for anything. The frc_direction
field is assigned, but never read.
Just remove it.

Differential Revision:	https://reviews.freebsd.org/D2773
Approved by:	philip (mentor)
2015-06-11 17:57:47 +00:00
Kristof Provost
837b925aba pf: Save the protocol number in the pf_fragment
When we try to look up a pf_fragment with pf_find_fragment() we compare (see
pf_frag_compare()) addresses (and family), id but also protocol.  We failed to
save the protocol to the pf_fragment in pf_fragcache(), resulting in failing
reassembly.

Differential Revision:	https://reviews.freebsd.org/D2772
2015-06-11 13:26:16 +00:00
Kristof Provost
0b7eba6ad4 pf: address family must be set when creating a pf_fragment
Fix a panic when handling fragmented ip4 packets with 'drop-ovl' set.
In that scenario we take a different branch in pf_normalize_ip(), taking us to
pf_fragcache() (rather than pf_reassemble()). In pf_fragcache() we create a
pf_fragment, but do not set the address family. This leads to a panic when we
try to insert that into pf_frag_tree because pf_addr_cmp(), which is used to
compare the pf_fragments doesn't know what to do if the address family is not
set.

Simply ensure that the address family is set correctly (always AF_INET in this
path).

PR:			200330
Differential Revision:	https://reviews.freebsd.org/D2769
Approved by:		philip (mentor), gnn (mentor)
2015-06-10 13:44:04 +00:00
Jung-uk Kim
fd90e2ed54 CALLOUT_MPSAFE has lost its meaning since r141428, i.e., for more than ten
years for head.  However, it is continuously misused as the mpsafe argument
for callout_init(9).  Deprecate the flag and clean up callout_init() calls
to make them more consistent.

Differential Revision:	https://reviews.freebsd.org/D2613
Reviewed by:	jhb
MFC after:	2 weeks
2015-05-22 17:05:21 +00:00
Gleb Smirnoff
3dd01a884c Use MTX_SYSINIT() instead of mtx_init() to separate mutex initialization
from associated structures initialization.  The mutexes are global, while
the structures are per-vnet.

Submitted by:	Nikos Vassiliadis <nvass gmx.com>
2015-05-19 14:04:21 +00:00
Gleb Smirnoff
30fe681e44 During module unload unlock rules before destroying UMA zones, which
may sleep in uma_drain(). It is safe to unlock here, since we are already
dehooked from pfil(9) and all pf threads had quit.

Sponsored by:	Nginx, Inc.
2015-05-19 14:02:40 +00:00
Gleb Smirnoff
78680d05d1 A miss from r283061: don't dereference NULL is pf_get_mtag() fails.
PR:		200222
Submitted by:	Franco Fichtner <franco opnsense.org>
2015-05-18 15:51:27 +00:00
Gleb Smirnoff
b7f69c506d Don't dereference NULL is pf_get_mtag() fails.
PR:		200222
Submitted by:	Franco Fichtner <franco opnsense.org>
2015-05-18 15:05:12 +00:00
Gleb Smirnoff
772e66a6fc Move ALTQ from contrib to net/altq. The ALTQ code is for many years
discontinued by its initial authors. In FreeBSD the code was already
slightly edited during the pf(4) SMP project. It is about to be edited
more in the projects/ifnet. Moving out of contrib also allows to remove
several hacks to the make glue.

Reviewed by:	net@
2015-04-16 20:22:40 +00:00
Kristof Provost
3d1bbe5fa0 pf: Fix forwarding detection
If the direction is not PF_OUT we can never be forwarding. Some input packets
have rcvif != ifp (looped back packets), which lead us to ip6_forward() inbound
packets, causing panics.

Equally, we need to ensure that packets were really received and not locally
generated before trying to ip6_forward() them.

Differential Revision:	https://reviews.freebsd.org/D2286
Approved by:		gnn(mentor)
2015-04-14 19:07:37 +00:00
George V. Neville-Neil
916e17fd56 I can find no reason to allow packets with both SYN and FIN bits
set past this point in the code. The packet should be dropped and
not massaged as it is here.

Differential Revision:  https://reviews.freebsd.org/D2266
Submitted by: eri
Sponsored by: Rubicon Communications (Netgate)
2015-04-14 14:43:42 +00:00
Kristof Provost
1873dcc8c9 pf: Skip firewall for refragmented ip6 packets
In cases where we scrub (fragment reassemble) on both input and output
we risk ending up in infinite loops when forwarding packets.

Fragmented packets come in and get collected until we can defragment. At
that point the defragmented packet is handed back to the ip stack (at
the pfil point in ip6_input(). Normal processing continues.

Eventually we figure out that the packet has to be forwarded and we end
up at the pfil hook in ip6_forward(). After doing the inspection on the
defragmented packet we see that the packet has been defragmented and
because we're forwarding we have to refragment it.

In pf_refragment6() we split the packet up again and then ip6_forward()
the individual fragments.  Those fragments hit the pfil hook on the way
out, so they're collected until we can reconstruct the full packet, at
which point we're right back where we left off and things continue until
we run out of stack.

Break that loop by marking the fragments generated by pf_refragment6()
as M_SKIP_FIREWALL. There's no point in processing those packets in the
firewall anyway. We've already filtered on the full packet.

Differential Revision:	https://reviews.freebsd.org/D2197
Reviewed by:	glebius, gnn
Approved by:	gnn (mentor)
2015-04-06 19:05:00 +00:00