associated with the syncache entry: in case tcp_close() has been
called on the corresponding listening socket, the lock has been
destroyed as a side effect of in_pcbdetach(), causing a panic when
we attempt to lock on it.
Reviewed by: hsu
the mbuf allocator flags {M_TRYWAIT, M_DONTWAIT}.
o Fix a bpf_compat issue where malloc() was defined to just call
bpf_alloc() and pass the 'canwait' flag(s) along. It's been changed
to call bpf_alloc() but pass the corresponding M_TRYWAIT or M_DONTWAIT
flag (and only one of those two).
Submitted by: Hiten Pandya <hiten@unixdaemons.com> (hiten->commit_count++)
apparent ack-on-ack problem with FreeBSD. Prof. Jacobson noticed a
case in our TCP stack which would acknowledge a received ack-only packet,
which is not legal in TCP.
Submitted by: Van Jacobson <van@packetdesign.com>,
bmah@packetdesign.com (Bruce A. Mah)
MFC after: 7 days
bridge.c nor if_ethersubr.c depend on IPFIREWALL.
Restore the use of fw_one_pass in if_ethersubr.c
ipfw.8 will be updated with a separate commit.
Approved by: re
so that it can be reused elsewhere (there is a number of places
where it can be useful). This also trims some 200 lines from
the body of ip_output(), which helps readability a bit.
(This change was discussed a few weeks ago on the mailing lists,
Julian agreed, silence from others. It is not a functional change,
so i expect it to be ok to commit it now but i am happy to back it
out if there are objections).
While at it, fix some function headers and replace m_copy() with
m_copypacket() where applicable.
MFC after: 1 week
Replace m_copy() with m_copypacket() where applicable.
Replace "if (a.s_addr ...)" with "if (a.s_addr != INADDR_ANY ...)"
to make it clear what the code means.
While at it, fix some function headers and remove 'register' from
variable declarations.
MFC after: 3 days
No functional changes, but:
+ the mrouting module now should behave the same as the compiled-in
version (it did not before, some of the rsvp code was not loaded
properly);
+ netinet/ip_mroute.c is now truly optional;
+ removed some redundant/unused code;
+ changed many instances of '0' to NULL and INADDR_ANY as appropriate;
+ removed several static variables to make the code more SMP-friendly;
+ fixed some minor bugs in the mrouting code (mostly, incorrect return
values from functions).
This commit is also a prerequisite to the addition of support for PIM,
which i would like to put in before DP2 (it does not change any of
the existing APIs, anyways).
Note, in the process we found out that some device drivers fail to
properly handle changes in IFF_ALLMULTI, leading to interesting
behaviour when a multicast router is started. This bug is not
corrected by this commit, and will be fixed with a separate commit.
Detailed changes:
--------------------
netinet/ip_mroute.c all the above.
conf/files make ip_mroute.c optional
net/route.c fix mrt_ioctl hook
netinet/ip_input.c fix ip_mforward hook, move rsvp_input() here
together with other rsvp code, and a couple
of indentation fixes.
netinet/ip_output.c fix ip_mforward and ip_mcast_src hooks
netinet/ip_var.h rsvp function hooks
netinet/raw_ip.c hooks for mrouting and rsvp functions, plus
interface cleanup.
netinet/ip_mroute.h remove an unused and optional field from a struct
Most of the code is from Pavlin Radoslavov and the XORP project
Reviewed by: sam
MFC after: 1 week
ipfw_flow_id structure actual size and bcmp(3) may fail to compare
them properly. Compare members of these structures instead.
PR: kern/44078
Submitted by: Oleg Bulyzhin <oleg@rinet.ru>
Reviewed by: luigi
MFC after: 2 weeks
o fix #ifdef typo
o must use "bounce functions" when dispatched from the protosw table
don't know how this stuff was missed in my testing; must've committed
the wrong bits
Pointy hat: sam
Submitted by: "Doug Ambrisko" <ambrisko@verniernetworks.com>
prediction code. Previously, 2GB worth of header predicted data
could leave these variables too far out of sequence which would cause
problems after receiving a packet that did not match the header
prediction.
Submitted by: Bill Baumann <bbaumann@isilon.com>
Sponsored by: Isilon Systems, Inc.
Reviewed by: hsu, pete@isilon.com, neal@isilon.com, aaronp@isilon.com
This allows socket() to return an error when the kernel is not built
with IPDIVERT, and doesn't prevent future applications from using the
"borrowed" IP protocol number. The sysctl net.inet.raw.olddiverterror
controls whether opening a socket with the "borrowed" IP protocol
fails with an accompanying kernel printf; this code should last only a
couple of releases.
Approved by: re
Quoting luigi:
In order to make the userland code fully 64-bit clean it may
be necessary to commit other changes that may or may not cause
a minor change in the ABI.
Reviewed by: luigi
to the primary local IP address when doing a TCP connect(). The
tcp_connect() code was relying on in_pcbconnect (actually in_pcbladdr)
modifying the passed-in sockaddr, and I failed to notice this in
the recent change that added in_pcbconnect_setup(). As a result,
tcp_connect() was ending up using the unmodified sockaddr address
instead of the munged version.
There are two cases to handle: if in_pcbconnect_setup() succeeds,
then the PCB has already been updated with the correct destination
address as we pass it pointers to inp_faddr and inp_fport directly.
If in_pcbconnect_setup() fails due to an existing but dead connection,
then copy the destination address from the old connection.
a server process bound to a wildcard UDP socket to select the IP
address from which outgoing packets are sent on a per-datagram
basis. When combined with IP_RECVDSTADDR, such a server process can
guarantee to reply to an incoming request using the same source IP
address as the destination IP address of the request, without having
to open one socket per server IP address.
Discussed on: -net
Approved by: re
to send datagrams from an unconnected socket, we used to first block
input, then connect the socket to the sendmsg/sendto destination,
send the datagram, and finally disconnect the socket and unblock
input.
We now use in_pcbconnect_setup() to check if a connect() would have
succeeded, but we never record the connection in the PCB (local
anonymous port allocation is still recorded, though). The result
from in_pcbconnect_setup() authorises the sending of the datagram
and selects the local address and port to use, so we just construct
the header and call ip_output().
Discussed on: -net
Approved by: re
in_pcbconnect() called in_pcbconnect_setup(). This version performs
all of the functions of in_pcbconnect() except for the final
committing of changes to the PCB. In the case of an EADDRINUSE error
it can also provide to the caller the PCB of the duplicate connection,
avoiding an extra in_pcblookup_hash() lookup in tcp_connect().
This change will allow the "temporary connect" hack in udp_output()
to be removed and is part of the preparation for adding the
IP_SENDSRCADDR control message.
Discussed on: -net
Approved by: re
Remove the never completed _IP_VHL version, it has not caught on
anywhere and it would make us incompatible with other BSD netstacks
to retain this version.
Add a CTASSERT protecting sizeof(struct ip) == 20.
Don't let the size of struct ipq depend on the IPDIVERT option.
This is a functional no-op commit.
Approved by: re
called in_pcbbind_setup() that does everything except commit the
changes to the PCB. There should be no functional change here, but
in_pcbbind_setup() will be used by the soon-to-appear IP_SENDSRCADDR
control message implementation to check or allocate the source
address and port.
Discussed on: -net
Approved by: re
- set IFF_UP on SIOCSIFADDR. be consistent with others.
- set if_addrlen explicitly (just in case)
- multi destination mode is long gone.
- missing break statement
- add gif_set_tunnel(), so that we can set tunnel address from within the
kernel at ease.
- encap_attach/detach dynamically on ioctls
- move encap_attach() to dedicated function in in*_gif.c
Obtained from: KAME
MFC after: 3 weeks
supposed to be checked by the firewall rules twice. However, because the
various ipsec handlers never call ip_input(), this never happens anyway.
This fixes the situation where a gif tunnel is encrypted with IPsec. In
such a case, after IPsec processing, the unencrypted contents from the
GIF tunnel are fed back to the ipintrq and subsequently handeld by
ip_input(). Yet, since there still is IPSec history attached, the
packets coming out from the gif device are never fed into the filtering
code.
This fix was sent to Itojun, and he pointed towartds
http://www.netbsd.org/Documentation/network/ipsec/#ipf-interaction.
This patch actually implements what is stated there (specifically:
Packet came from tunnel devices (gif(4) and ipip(4)) will still
go through ipf(4). You may need to identify these packets by
using interface name directive in ipf.conf(5).
Reviewed by: rwatson
MFC after: 3 weeks
configuration stuff as well as conditional code in the IPv4 and IPv6
areas. Everything is conditional on FAST_IPSEC which is mutually
exclusive with IPSEC (KAME IPsec implmentation).
As noted previously, don't use FAST_IPSEC with INET6 at the moment.
Reviewed by: KAME, rwatson
Approved by: silence
Supported by: Vernier Networks
o instead of a list of mbufs use a list of m_tag structures a la openbsd
o for netgraph et. al. extend the stock openbsd m_tag to include a 32-bit
ABI/module number cookie
o for openbsd compatibility define a well-known cookie MTAG_ABI_COMPAT and
use this in defining openbsd-compatible m_tag_find and m_tag_get routines
o rewrite KAME use of aux mbufs in terms of packet tags
o eliminate the most heavily used aux mbufs by adding an additional struct
inpcb parameter to ip_output and ip6_output to allow the IPsec code to
locate the security policy to apply to outbound packets
o bump __FreeBSD_version so code can be conditionalized
o fixup ipfilter's call to ip_output based on __FreeBSD_version
Reviewed by: julian, luigi (silent), -arch, -net, darren
Approved by: julian, silence from everyone else
Obtained from: openbsd (mostly)
MFC after: 1 month
timestamped TCP packets where FreeBSD will send DATA+FIN and
A W2K box will ack just the DATA portion. If this occurs
after FreeBSD has done a (NewReno) fast-retransmit and is
recovering it (dupacks > threshold) it triggers a case in
tcp_newreno_partial_ack() (tcp_newreno() in stable) where
tcp_output() is called with the expectation that the retransmit
timer will be reloaded. But tcp_output() falls through and
returns without doing anything, causing the persist timer to be
loaded instead. This causes the connection to hang until W2K gives up.
This occurs because in the case where only the FIN must be acked, the
'len' calculation in tcp_output() will be 0, a lot of checks will be
skipped, and the FIN check will also be skipped because it is designed
to handle FIN retransmits, not forced transmits from tcp_newreno().
The solution is to simply set TF_ACKNOW before calling tcp_output()
to absolute guarentee that it will run the send code and reset the
retransmit timer. TF_ACKNOW is already used for this purpose in other
cases.
For some unknown reason this patch also seems to greatly reduce
the number of duplicate acks received when Guido runs his tests over
a lossy network. It is quite possible that there are other
tcp_newreno{_partial_ack()} cases which were not generating the expected
output which this patch also fixes.
X-MFC after: Will be MFC'd after the freeze is over
o Move len initialization closer to place of its first usage.
o Compare len with 0 to improve readability.
o Explicitly zero out phlen in ip_insertoptions() in failure case.
Suggested by: jhb
Reviewed by: jhb
MFC after: 2 weeks
Windows 2000 box and a FreeBSD box could stall. The problem turned out
to be a timestamp reply bug in the W2K TCP stack. FreeBSD sends a
timestamp with the SYN, W2K returns a timestamp of 0 in the SYN+ACK
causing FreeBSD to calculate an insane SRTT and RTT, resulting in
a maximal retransmit timeout (60 seconds). If there is any packet
loss on the connection for the first six or so packets the retransmit
case may be hit (the window will still be too small for fast-retransmit),
causing a 60+ second pause. The W2K box gives up and closes the
connection.
This commit works around the W2K bug.
15:04:59.374588 FREEBSD.20 > W2K.1036: S 1420807004:1420807004(0) win 65535 <mss 1460,nop,wscale 2,nop,nop,timestamp 188297344 0> (DF) [tos 0x8]
15:04:59.377558 W2K.1036 > FREEBSD.20: S 4134611565:4134611565(0) ack 1420807005 win 17520 <mss 1460,nop,wscale 0,nop,nop,timestamp 0 0> (DF)
Bug reported by: Guido van Rooij <guido@gvr.org>
packets in addition to IPPROTO_IPV4 and IPPROTO_IPV6, explicitly specify
IPPROTO_IPV4 or IPPROTO_IPV6 instead of -1 when calling encap_attach().
MFC after: 28 days
(along with other if_gre changes)
- use `struct uma_zone *' instead of uma_zone_t, so that <sys/uma.h> isn't
a prerequisite.
- don't include <sys/uma.h>.
Namespace pollution makes "opaque" types like uma_zone_t perfectly
non-opaque. Such types should never be used (see style(9)).
Fixed subsequently grwon dependencies of this header on its own pollution:
- include <sys/_mutex.h> and its prerequisite <sys/_lock.h> instead of
depending on namespace pollution 2 layers deep in <sys/uma.h>.
firewall logging on and off when at elevated securelevel(8). It would
be nice to be able to only lock these at securelevel >= 3, like rules
are, but there is no such functionality at present. I don't see reason
to be adding features to securelevel(8) with MAC being merged into 5.0.
PR: kern/39396
Reviewed by: luigi
MFC after: 1 week
called <machine/_types.h>.
o <machine/ansi.h> will continue to live so it can define MD clock
macros, which are only MD because of gratuitous differences between
architectures.
o Change all headers to make use of this. This mainly involves
changing:
#ifdef _BSD_FOO_T_
typedef _BSD_FOO_T_ foo_t;
#undef _BSD_FOO_T_
#endif
to:
#ifndef _FOO_T_DECLARED
typedef __foo_t foo_t;
#define _FOO_T_DECLARED
#endif
Concept by: bde
Reviewed by: jake, obrien
in6_v4mapsin6_sockaddr() which allocate the appropriate sockaddr_in*
structure and initialize it with the address and port information passed
as arguments. Use calls to these new functions to replace code that is
replicated multiple times in in_setsockaddr(), in_setpeeraddr(),
in6_setsockaddr(), in6_setpeeraddr(), in6_mapped_sockaddr(), and
in6_mapped_peeraddr(). Inline COMMON_END in tcp_usr_accept() so that
we can call in_sockaddr() with temporary copies of the address and port
after the PCB is unlocked.
Fix the lock violation in tcp6_usr_accept() (caused by calling MALLOC()
inside in6_mapped_peeraddr() while the PCB is locked) by changing
the implementation of tcp6_usr_accept() to match tcp_usr_accept().
Reviewed by: suz
not meant to duplicate) TCP/Vegas. Add four sysctls and default the
implementation to 'off'.
net.inet.tcp.inflight_enable enable algorithm (defaults to 0=off)
net.inet.tcp.inflight_debug debugging (defaults to 1=on)
net.inet.tcp.inflight_min minimum window limit
net.inet.tcp.inflight_max maximum window limit
MFC after: 1 week
Implement the M_SKIP_FIREWALL bit in m_flags to avoid loops
for firewall-generated packets (the constant has to go in sys/mbuf.h).
Better comments on keepalive generation, and enforce dyn_rst_lifetime
and dyn_fin_lifetime to be less than dyn_keepalive_period.
Enforce limits (up to 64k) on the number of dynamic buckets, and
retry allocation with smaller sizes.
Raise default number of dynamic rules to 4096.
Improved handling of set of rules -- now you can atomically
enable/disable multiple sets, move rules from one set to another,
and swap sets.
sbin/ipfw/ipfw2.c:
userland support for "noerror" pipe attribute.
userland support for sets of rules.
minor improvements on rule parsing and printing.
sbin/ipfw/ipfw.8:
more documentation on ipfw2 extensions, differences from ipfw1
(so we can use the same manpage for both), stateful rules,
and some additional examples.
Feedback and more examples needed here.
we can use the names _receive() and _send() for the receive() and send()
checks. Rename related constants, policy implementations, etc.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
When a pipe or queue has the "noerror" attribute, do not report
drops to the caller (ip_output() and friends).
(2 lines to implement it, 2 lines to document it.)
This will let you simulate losses on the sender side as if they
happened in the middle of the network, i.e. with no explicit feedback
to the sender.
manpage and ipfw2.c changes to follow shortly, together with other
ipfw2 changes.
Requested by: silby
MFC after: 3 days
satisfy consumers of ip_var.h that need a complete definition of
struct ipq and don't include mac.h.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
The bugfix (ipfw2.c) makes the handling of port numbers with
a dash in the name, e.g. ftp-data, consistent with old ipfw:
use \\ before the - to consider it as part of the name and not
a range separator.
The new feature (all this description will go in the manpage):
each rule now belongs to one of 32 different sets, which can
be optionally specified in the following form:
ipfw add 100 set 23 allow ip from any to any
If "set N" is not specified, the rule belongs to set 0.
Individual sets can be disabled, enabled, and deleted with the commands:
ipfw disable set N
ipfw enable set N
ipfw delete set N
Enabling/disabling of a set is atomic. Rules belonging to a disabled
set are skipped during packet matching, and they are not listed
unless you use the '-S' flag in the show/list commands.
Note that dynamic rules, once created, are always active until
they expire or their parent rule is deleted.
Set 31 is reserved for the default rule and cannot be disabled.
All sets are enabled by default. The enable/disable status of the sets
can be shown with the command
ipfw show sets
Hopefully, this feature will make life easier to those who want to
have atomic ruleset addition/deletion/tests. Examples:
To add a set of rules atomically:
ipfw disable set 18
ipfw add ... set 18 ... # repeat as needed
ipfw enable set 18
To delete a set of rules atomically
ipfw disable set 18
ipfw delete set 18
ipfw enable set 18
To test a ruleset and disable it and regain control if something
goes wrong:
ipfw disable set 18
ipfw add ... set 18 ... # repeat as needed
ipfw enable set 18 ; echo "done "; sleep 30 && ipfw disable set 18
here if everything goes well, you press control-C before
the "sleep" terminates, and your ruleset will be left
active. Otherwise, e.g. if you cannot access your box,
the ruleset will be disabled after the sleep terminates.
I think there is only one more thing that one might want, namely
a command to assign all rules in set X to set Y, so one can
test a ruleset using the above mechanisms, and once it is
considered acceptable, make it part of an existing ruleset.
case, also preserve the MAC label. Note that this mbuf allocation
is fairly non-optimal, but not my fault.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
Add MAC support for the UDP protocol. Invoke appropriate MAC entry
points to label packets that are generated by local UDP sockets,
and to authorize delivery of mbufs to local sockets both in the
multicast/broadcast case and the unicast case.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
pointer and incoming mbuf pointer will be non-NULL in tcp_respond().
This is relied on by the MAC code for correctness, as well as
existing code.
Obtained from: TrustedBSD PRoject
Sponsored by: DARPA, NAI Labs
kernel access control.
Add support for labeling most out-going ICMP messages using an
appropriate MAC entry point. Currently, we do not explicitly
label packet reflect (timestamp, echo request) ICMP events,
implicitly using the originating packet label since the mbuf is
reused. This will be made explicit at some point.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
Instrument the TCP socket code for packet generation and delivery:
label outgoing mbufs with the label of the socket, and check socket and
mbuf labels before permitting delivery to a socket. Assign labels
to newly accepted connections when the syncache/cookie code has done
its business. Also set peer labels as convenient. Currently,
MAC policies cannot influence the PCB matching algorithm, so cannot
implement polyinstantiation. Note that there is at least one case
where a PCB is not available due to the TCP packet not being associated
with any socket, so we don't label in that case, but need to handle
it in a special manner.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
Instrument the raw IP socket code for packet generation and delivery:
label outgoing mbufs with the label of the socket, and check the
socket and mbuf labels before permitting delivery to a socket,
permitting MAC policies to selectively allow delivery of raw IP mbufs
to various raw IP sockets that may be open. Restructure the policy
checking code to compose IPsec and MAC results in a more readable
manner.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
When fragmenting an IP datagram, invoke an appropriate MAC entry
point so that MAC labels may be copied (...) to the individual
IP fragment mbufs by MAC policies.
When IP options are inserted into an IP datagram when leaving a
host, preserve the label if we need to reallocate the mbuf for
alignment or size reasons.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
Instrument the code managing IP fragment reassembly queues (struct ipq)
to invoke appropriate MAC entry points to maintain a MAC label on
each queue. Permit MAC policies to associate information with a queue
based on the mbuf that caused it to be created, update that information
based on further mbufs accepted by the queue, influence the decision
making process by which mbufs are accepted to the queue, and set the
label of the mbuf holding the reassembled datagram following reassembly
completetion.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
When generating an IGMP message, invoke a MAC entry point to permit
the MAC framework to label its mbuf appropriately for the target
interface.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
When generating an ARP query, invoke a MAC entry point to permit the
MAC framework to label its mbuf appropriately for the interface.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
kernel access control.
Invoke the MAC framework to label mbuf created using divert sockets.
These labels may later be used for access control on delivery to
another socket, or to an interface.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI LAbs
kernel access control.
Label IP fragment reassembly queues, permitting security features to
be maintained on those objects. ipq_label will be used to manage
the reassembly of fragments into IP datagrams using security
properties. This permits policies to deny the reassembly of fragments,
as well as influence the resulting label of a datagram following
reassembly.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
SYSCTL_OUT() from blocking while locks are held. This should
only be done when it would be inconvenient to make a temporary copy of
the data and defer calling SYSCTL_OUT() until after the locks are
released.
data structures pick up security and synchronization primitives, it
becomes increasingly desirable not to arbitrarily export them via
include files to userland, as the userland applications pick up new
#include dependencies.
Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs
net.inet.tcp.rexmit_min (default 3 ticks equiv)
This sysctl is the retransmit timer RTO minimum,
specified in milliseconds. This value is
designed for algorithmic stability only.
net.inet.tcp.rexmit_slop (default 200ms)
This sysctl is the retransmit timer RTO slop
which is added to every retransmit timeout and
is designed to handle protocol stack overheads
and delayed ack issues.
Note that the *original* code applied a 1-second
RTO minimum but never applied real slop to the RTO
calculation, so any RTO calculation over one second
would have no slop and thus not account for
protocol stack overheads (TCP timestamps are not
a measure of protocol turnaround!). Essentially,
the original code made the RTO calculation almost
completely irrelevant.
Please note that the 200ms slop is debateable.
This commit is not meant to be a line in the sand,
and if the community winds up deciding that increasing
it is the correct solution then it's easy to do.
Note that larger values will destroy performance
on lossy networks while smaller values may result in
a greater number of unnecessary retransmits.
one second but it badly breaks throughput on networks with minor packet
loss.
Complaints by: at least two people tracked down to this.
MFC after: 3 days
just because you leave your session idle.
Also, put in a fix for 64-bit architectures (to be revised).
In detail:
ip_fw.h
* Reorder fields in struct ip_fw to avoid alignment problems on
64-bit machines. This only masks the problem, I am still not
sure whether I am doing something wrong in the code or there
is a problem elsewhere (e.g. different aligmnent of structures
between userland and kernel because of pragmas etc.)
* added fields in dyn_rule to store ack numbers, so we can
generate keepalives when the dynamic rule is about to expire
ip_fw2.c
* use a local function, send_pkt(), to generate TCP RST for Reset rules;
* save about 250 bytes by cleaning up the various snprintf()
in ipfw_log() ...
* ... and use twice as many bytes to implement keepalives
(this seems to be working, but i have not tested it extensively).
Keepalives are generated once every 5 seconds for the last 20 seconds
of the lifetime of a dynamic rule for an established TCP flow. The
packets are sent to both sides, so if at least one of the endpoints
is responding, the timeout is refreshed and the rule will not expire.
You can disable this feature with
sysctl net.inet.ip.fw.dyn_keepalive=0
(the default is 1, to have them enabled).
MFC after: 1 day
(just kidding... I will supply an updated version of ipfw2 for
RELENG_4 tomorrow).
This was always broken in HEAD (the offending statement was introduced
in rev. 1.123 for HEAD, while RELENG_4 included this fix (in rev.
1.99.2.12 for RELENG_4) and I inadvertently deleted it in 1.99.2.30.
So I am also restoring these two lines in RELENG_4 now.
We might need another few things from 1.99.2.30.
