linux-toradex.git/net/ipv4/ip_output.c, branch v3.13.1

ipv4: consistent reporting of pmtu data in case of corking

2013-12-22T23:52:09+00:00

We report different pmtu values back on the first write and on further
writes on an corked socket.

Also don't include the dst.header_len (respectively exthdrlen) as this
should already be dealt with by the interface mtu of the outgoing
(virtual) interface and policy of that interface should dictate if
fragmentation should happen.

Instead reduce the pmtu data by IP options as we do for IPv6. Make the
same changes for ip_append_data, where we did not care about options or
dst.header_len at all.

Signed-off-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller

ipv4: introduce new IP_MTU_DISCOVER mode IP_PMTUDISC_INTERFACE

2013-11-06T02:52:27+00:00

Sockets marked with IP_PMTUDISC_INTERFACE won't do path mtu discovery,
their sockets won't accept and install new path mtu information and they
will always use the interface mtu for outgoing packets. It is guaranteed
that the packet is not fragmented locally. But we won't set the DF-Flag
on the outgoing frames.

Florian Weimer had the idea to use this flag to ensure DNS servers are
never generating outgoing fragments. They may well be fragmented on the
path, but the server never stores or usees path mtu values, which could
well be forged in an attack.

(The root of the problem with path MTU discovery is that there is
no reliable way to authenticate ICMP Fragmentation Needed But DF Set
messages because they are sent from intermediate routers with their
source addresses, and the IMCP payload will not always contain sufficient
information to identify a flow.)

Recent research in the DNS community showed that it is possible to
implement an attack where DNS cache poisoning is feasible by spoofing
fragments. This work was done by Amir Herzberg and Haya Shulman:


This issue was previously discussed among the DNS community, e.g.
,
without leading to fixes.

This patch depends on the patch "ipv4: fix DO and PROBE pmtu mode
regarding local fragmentation with UFO/CORK" for the enforcement of the
non-fragmentable checks. If other users than ip_append_page/data should
use this semantic too, we have to add a new flag to IPCB(skb)->flags to
suppress local fragmentation and check for this in ip_finish_output.

Many thanks to Florian Weimer for the idea and feedback while implementing
this patch.

Cc: David S. Miller 
Suggested-by: Florian Weimer 
Signed-off-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller

ipv4: fix DO and PROBE pmtu mode regarding local fragmentation with UFO/CORK

2013-10-29T04:15:22+00:00

UFO as well as UDP_CORK do not respect IP_PMTUDISC_DO and
IP_PMTUDISC_PROBE well enough.

UFO enabled packet delivery just appends all frags to the cork and hands
it over to the network card. So we just deliver non-DF udp fragments
(DF-flag may get overwritten by hardware or virtual UFO enabled
interface).

UDP_CORK does enqueue the data until the cork is disengaged. At this
point it sets the correct IP_DF and local_df flags and hands it over to
ip_fragment which in this case will generate an icmp error which gets
appended to the error socket queue. This is not reflected in the syscall
error (of course, if UFO is enabled this also won't happen).

Improve this by checking the pmtudisc flags before appending data to the
socket and if we still can fit all data in one packet when IP_PMTUDISC_DO
or IP_PMTUDISC_PROBE is set, only then proceed.

We use (mtu-fragheaderlen) to check for the maximum length because we
ensure not to generate a fragment and non-fragmented data does not need
to have its length aligned on 64 bit boundaries. Also the passed in
ip_options are already aligned correctly.

Maybe, we can relax some other checks around ip_fragment. This needs
more research.

Signed-off-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

2013-10-23T20:49:34+00:00

Conflicts:
	drivers/net/usb/qmi_wwan.c
	include/net/dst.h

Trivial merge conflicts, both were overlapping changes.

Signed-off-by: David S. Miller

ip_output: do skb ufo init for peeked non ufo skb as well

2013-10-19T23:20:52+00:00

Now, if user application does:
sendto lenmtu flag 0
The skb is not treated as fragmented one because it is not initialized
that way. So move the initialization to fix this.

introduced by:
commit e89e9cf539a28df7d0eb1d0a545368e9920b34ac "[IPv4/IPv6]: UFO Scatter-gather approach"

Signed-off-by: Jiri Pirko 
Acked-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller

ipv4: processing ancillary IP_TOS or IP_TTL

2013-09-28T22:21:52+00:00

If IP_TOS or IP_TTL are specified as ancillary data, then sendmsg() sends out
packets with the specified TTL or TOS overriding the socket values specified
with the traditional setsockopt().

The struct inet_cork stores the values of TOS, TTL and priority that are
passed through the struct ipcm_cookie. If there are user-specified TOS
(tos != -1) or TTL (ttl != 0) in the struct ipcm_cookie, these values are
used to override the per-socket values. In case of TOS also the priority
is changed accordingly.

Two helper functions get_rttos and get_rtconn_flags are defined to take
into account the presence of a user specified TOS value when computing
RT_TOS and RT_CONN_FLAGS.

Signed-off-by: Francesco Fusco 
Signed-off-by: David S. Miller

ip: generate unique IP identificator if local fragmentation is allowed

2013-09-19T18:11:15+00:00

If local fragmentation is allowed, then ip_select_ident() and
ip_select_ident_more() need to generate unique IDs to ensure
correct defragmentation on the peer.

For example, if IPsec (tunnel mode) has to encrypt large skbs
that have local_df bit set, then all IP fragments that belonged
to different ESP datagrams would have used the same identificator.
If one of these IP fragments would get lost or reordered, then
peer could possibly stitch together wrong IP fragments that did
not belong to the same datagram. This would lead to a packet loss
or data corruption.

Signed-off-by: Ansis Atteka 
Signed-off-by: David S. Miller

ip: use ip_hdr() in __ip_make_skb() to retrieve IP header

2013-09-19T18:11:15+00:00

skb->data already points to IP header, but for the sake of
consistency we can also use ip_hdr() to retrieve it.

Signed-off-by: Ansis Atteka 
Signed-off-by: David S. Miller

xfrm: introduce helper for safe determination of mtu

2013-08-14T11:09:07+00:00

skb->sk socket can be of AF_INET or AF_INET6 address family. Thus we
always have to make sure we a referring to the correct interpretation
of skb->sk.

We only depend on header defines to query the mtu, so we don't introduce
a new dependency to ipv6 by this change.

Cc: Steffen Klassert 
Signed-off-by: Hannes Frederic Sowa 
Signed-off-by: Steffen Klassert

ipv4: ip_output: remove inline marking of EXPORT_SYMBOL functions

2013-05-11T23:12:44+00:00

EXPORT_SYMBOL and inline directives are contradictory to each other.
The patch fixes this inconsistency.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Denis Efremov 
Signed-off-by: David S. Miller