<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux.git/include/linux/skbuff.h, branch v5.9-rc4</title>
<subtitle>Linux kernel source tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/'/>
<entry>
<title>Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net</title>
<updated>2020-09-04T01:50:48+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2020-09-04T01:50:48+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=3e8d3bdc2a757cc6be5470297947799a7df445cc'/>
<id>3e8d3bdc2a757cc6be5470297947799a7df445cc</id>
<content type='text'>
Pull networking fixes from David Miller:

 1) Use netif_rx_ni() when necessary in batman-adv stack, from Jussi
    Kivilinna.

 2) Fix loss of RTT samples in rxrpc, from David Howells.

 3) Memory leak in hns_nic_dev_probe(), from Dignhao Liu.

 4) ravb module cannot be unloaded, fix from Yuusuke Ashizuka.

 5) We disable BH for too lokng in sctp_get_port_local(), add a
    cond_resched() here as well, from Xin Long.

 6) Fix memory leak in st95hf_in_send_cmd, from Dinghao Liu.

 7) Out of bound access in bpf_raw_tp_link_fill_link_info(), from
    Yonghong Song.

 8) Missing of_node_put() in mt7530 DSA driver, from Sumera
    Priyadarsini.

 9) Fix crash in bnxt_fw_reset_task(), from Michael Chan.

10) Fix geneve tunnel checksumming bug in hns3, from Yi Li.

11) Memory leak in rxkad_verify_response, from Dinghao Liu.

12) In tipc, don't use smp_processor_id() in preemptible context. From
    Tuong Lien.

13) Fix signedness issue in mlx4 memory allocation, from Shung-Hsi Yu.

14) Missing clk_disable_prepare() in gemini driver, from Dan Carpenter.

15) Fix ABI mismatch between driver and firmware in nfp, from Louis
    Peens.

* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (110 commits)
  net/smc: fix sock refcounting in case of termination
  net/smc: reset sndbuf_desc if freed
  net/smc: set rx_off for SMCR explicitly
  net/smc: fix toleration of fake add_link messages
  tg3: Fix soft lockup when tg3_reset_task() fails.
  doc: net: dsa: Fix typo in config code sample
  net: dp83867: Fix WoL SecureOn password
  nfp: flower: fix ABI mismatch between driver and firmware
  tipc: fix shutdown() of connectionless socket
  ipv6: Fix sysctl max for fib_multipath_hash_policy
  drivers/net/wan/hdlc: Change the default of hard_header_len to 0
  net: gemini: Fix another missing clk_disable_unprepare() in probe
  net: bcmgenet: fix mask check in bcmgenet_validate_flow()
  amd-xgbe: Add support for new port mode
  net: usb: dm9601: Add USB ID of Keenetic Plus DSL
  vhost: fix typo in error message
  net: ethernet: mlx4: Fix memory allocation in mlx4_buddy_init()
  pktgen: fix error message with wrong function name
  net: ethernet: ti: am65-cpsw: fix rmii 100Mbit link mode
  cxgb4: fix thermal zone device registration
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull networking fixes from David Miller:

 1) Use netif_rx_ni() when necessary in batman-adv stack, from Jussi
    Kivilinna.

 2) Fix loss of RTT samples in rxrpc, from David Howells.

 3) Memory leak in hns_nic_dev_probe(), from Dignhao Liu.

 4) ravb module cannot be unloaded, fix from Yuusuke Ashizuka.

 5) We disable BH for too lokng in sctp_get_port_local(), add a
    cond_resched() here as well, from Xin Long.

 6) Fix memory leak in st95hf_in_send_cmd, from Dinghao Liu.

 7) Out of bound access in bpf_raw_tp_link_fill_link_info(), from
    Yonghong Song.

 8) Missing of_node_put() in mt7530 DSA driver, from Sumera
    Priyadarsini.

 9) Fix crash in bnxt_fw_reset_task(), from Michael Chan.

10) Fix geneve tunnel checksumming bug in hns3, from Yi Li.

11) Memory leak in rxkad_verify_response, from Dinghao Liu.

12) In tipc, don't use smp_processor_id() in preemptible context. From
    Tuong Lien.

13) Fix signedness issue in mlx4 memory allocation, from Shung-Hsi Yu.

14) Missing clk_disable_prepare() in gemini driver, from Dan Carpenter.

15) Fix ABI mismatch between driver and firmware in nfp, from Louis
    Peens.

* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (110 commits)
  net/smc: fix sock refcounting in case of termination
  net/smc: reset sndbuf_desc if freed
  net/smc: set rx_off for SMCR explicitly
  net/smc: fix toleration of fake add_link messages
  tg3: Fix soft lockup when tg3_reset_task() fails.
  doc: net: dsa: Fix typo in config code sample
  net: dp83867: Fix WoL SecureOn password
  nfp: flower: fix ABI mismatch between driver and firmware
  tipc: fix shutdown() of connectionless socket
  ipv6: Fix sysctl max for fib_multipath_hash_policy
  drivers/net/wan/hdlc: Change the default of hard_header_len to 0
  net: gemini: Fix another missing clk_disable_unprepare() in probe
  net: bcmgenet: fix mask check in bcmgenet_validate_flow()
  amd-xgbe: Add support for new port mode
  net: usb: dm9601: Add USB ID of Keenetic Plus DSL
  vhost: fix typo in error message
  net: ethernet: mlx4: Fix memory allocation in mlx4_buddy_init()
  pktgen: fix error message with wrong function name
  net: ethernet: ti: am65-cpsw: fix rmii 100Mbit link mode
  cxgb4: fix thermal zone device registration
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>net: Fix some comments</title>
<updated>2020-08-27T14:55:59+00:00</updated>
<author>
<name>Miaohe Lin</name>
<email>linmiaohe@huawei.com</email>
</author>
<published>2020-08-27T11:27:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=645f08975f49441b3e753d8dc5b740cbcb226594'/>
<id>645f08975f49441b3e753d8dc5b740cbcb226594</id>
<content type='text'>
Fix some comments, including wrong function name, duplicated word and so
on.

Signed-off-by: Miaohe Lin &lt;linmiaohe@huawei.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Fix some comments, including wrong function name, duplicated word and so
on.

Signed-off-by: Miaohe Lin &lt;linmiaohe@huawei.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: Get rid of consume_skb when tracing is off</title>
<updated>2020-08-24T23:12:26+00:00</updated>
<author>
<name>Herbert Xu</name>
<email>herbert@gondor.apana.org.au</email>
</author>
<published>2020-08-21T22:23:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=be769db2f95861cc8c7c8fedcc71a8c39b803b10'/>
<id>be769db2f95861cc8c7c8fedcc71a8c39b803b10</id>
<content type='text'>
The function consume_skb is only meaningful when tracing is enabled.
This patch makes it conditional on CONFIG_TRACEPOINTS.

Signed-off-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The function consume_skb is only meaningful when tracing is enabled.
This patch makes it conditional on CONFIG_TRACEPOINTS.

Signed-off-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>treewide: Use fallthrough pseudo-keyword</title>
<updated>2020-08-23T22:36:59+00:00</updated>
<author>
<name>Gustavo A. R. Silva</name>
<email>gustavoars@kernel.org</email>
</author>
<published>2020-08-23T22:36:59+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=df561f6688fef775baa341a0f5d960becd248b11'/>
<id>df561f6688fef775baa341a0f5d960becd248b11</id>
<content type='text'>
Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva &lt;gustavoars@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva &lt;gustavoars@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs</title>
<updated>2020-08-08T04:14:30+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2020-08-08T04:14:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=b79675e15a754ca51b9fc631e0961ccdd4ec3fc7'/>
<id>b79675e15a754ca51b9fc631e0961ccdd4ec3fc7</id>
<content type='text'>
Pull misc vfs updates from Al Viro:
 "No common topic whatsoever in those, sorry"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: define inode flags using bit numbers
  iov_iter: Move unnecessary inclusion of crypto/hash.h
  dlmfs: clean up dlmfs_file_{read,write}() a bit
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull misc vfs updates from Al Viro:
 "No common topic whatsoever in those, sorry"

* 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: define inode flags using bit numbers
  iov_iter: Move unnecessary inclusion of crypto/hash.h
  dlmfs: clean up dlmfs_file_{read,write}() a bit
</pre>
</div>
</content>
</entry>
<entry>
<title>net/sched: act_ct: fix miss set mru for ovs after defrag in act_ct</title>
<updated>2020-08-03T22:04:48+00:00</updated>
<author>
<name>wenxu</name>
<email>wenxu@ucloud.cn</email>
</author>
<published>2020-07-31T02:45:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=038ebb1a713d114d54dbf14868a73181c0c92758'/>
<id>038ebb1a713d114d54dbf14868a73181c0c92758</id>
<content type='text'>
When openvswitch conntrack offload with act_ct action. Fragment packets
defrag in the ingress tc act_ct action and miss the next chain. Then the
packet pass to the openvswitch datapath without the mru. The over
mtu packet will be dropped in output action in openvswitch for over mtu.

"kernel: net2: dropped over-mtu packet: 1528 &gt; 1500"

This patch add mru in the tc_skb_ext for adefrag and miss next chain
situation. And also add mru in the qdisc_skb_cb. The act_ct set the mru
to the qdisc_skb_cb when the packet defrag. And When the chain miss,
The mru is set to tc_skb_ext which can be got by ovs datapath.

Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
Signed-off-by: wenxu &lt;wenxu@ucloud.cn&gt;
Reviewed-by: Cong Wang &lt;xiyou.wangcong@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When openvswitch conntrack offload with act_ct action. Fragment packets
defrag in the ingress tc act_ct action and miss the next chain. Then the
packet pass to the openvswitch datapath without the mru. The over
mtu packet will be dropped in output action in openvswitch for over mtu.

"kernel: net2: dropped over-mtu packet: 1528 &gt; 1500"

This patch add mru in the tc_skb_ext for adefrag and miss next chain
situation. And also add mru in the qdisc_skb_cb. The act_ct set the mru
to the qdisc_skb_cb when the packet defrag. And When the chain miss,
The mru is set to tc_skb_ext which can be got by ovs datapath.

Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
Signed-off-by: wenxu &lt;wenxu@ucloud.cn&gt;
Reviewed-by: Cong Wang &lt;xiyou.wangcong@gmail.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net/flow_dissector: add packet hash dissection</title>
<updated>2020-07-24T22:23:31+00:00</updated>
<author>
<name>Ariel Levkovich</name>
<email>lariel@mellanox.com</email>
</author>
<published>2020-07-22T22:03:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=0cb09aff9d49d92305c3969fc84b785117412968'/>
<id>0cb09aff9d49d92305c3969fc84b785117412968</id>
<content type='text'>
Retreive a hash value from the SKB and store it
in the dissector key for future matching.

Signed-off-by: Ariel Levkovich &lt;lariel@mellanox.com&gt;
Reviewed-by: Jiri Pirko &lt;jiri@mellanox.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Retreive a hash value from the SKB and store it
in the dissector key for future matching.

Signed-off-by: Ariel Levkovich &lt;lariel@mellanox.com&gt;
Reviewed-by: Jiri Pirko &lt;jiri@mellanox.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>net: skbuff.h: drop duplicate words in comments</title>
<updated>2020-07-16T03:28:42+00:00</updated>
<author>
<name>Randy Dunlap</name>
<email>rdunlap@infradead.org</email>
</author>
<published>2020-07-15T16:42:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=2ff17117e60572d6974c766d6b1a225ec7d68795'/>
<id>2ff17117e60572d6974c766d6b1a225ec7d68795</id>
<content type='text'>
Drop doubled words in several comments.

Signed-off-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Cc: "David S. Miller" &lt;davem@davemloft.net&gt;
Cc: netdev@vger.kernel.org
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Drop doubled words in several comments.

Signed-off-by: Randy Dunlap &lt;rdunlap@infradead.org&gt;
Cc: "David S. Miller" &lt;davem@davemloft.net&gt;
Cc: netdev@vger.kernel.org
Signed-off-by: Jakub Kicinski &lt;kuba@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>iov_iter: Move unnecessary inclusion of crypto/hash.h</title>
<updated>2020-06-30T13:34:23+00:00</updated>
<author>
<name>Herbert Xu</name>
<email>herbert@gondor.apana.org.au</email>
</author>
<published>2020-06-12T06:57:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=7999096fa9cfd0253497c8d2ed9a5a1537521d25'/>
<id>7999096fa9cfd0253497c8d2ed9a5a1537521d25</id>
<content type='text'>
The header file linux/uio.h includes crypto/hash.h which pulls in
most of the Crypto API.  Since linux/uio.h is used throughout the
kernel this means that every tiny bit of change to the Crypto API
causes the entire kernel to get rebuilt.

This patch fixes this by moving it into lib/iov_iter.c instead
where it is actually used.

This patch also fixes the ifdef to use CRYPTO_HASH instead of just
CRYPTO which does not guarantee the existence of ahash.

Unfortunately a number of drivers were relying on linux/uio.h to
provide access to linux/slab.h.  This patch adds inclusions of
linux/slab.h as detected by build failures.

Also skbuff.h was relying on this to provide a declaration for
ahash_request.  This patch adds a forward declaration instead.

Signed-off-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The header file linux/uio.h includes crypto/hash.h which pulls in
most of the Crypto API.  Since linux/uio.h is used throughout the
kernel this means that every tiny bit of change to the Crypto API
causes the entire kernel to get rebuilt.

This patch fixes this by moving it into lib/iov_iter.c instead
where it is actually used.

This patch also fixes the ifdef to use CRYPTO_HASH instead of just
CRYPTO which does not guarantee the existence of ahash.

Unfortunately a number of drivers were relying on linux/uio.h to
provide access to linux/slab.h.  This patch adds inclusions of
linux/slab.h as detected by build failures.

Also skbuff.h was relying on this to provide a declaration for
ahash_request.  This patch adds a forward declaration instead.

Signed-off-by: Herbert Xu &lt;herbert@gondor.apana.org.au&gt;
Signed-off-by: Al Viro &lt;viro@zeniv.linux.org.uk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>bpf: Fix up bpf_skb_adjust_room helper's skb csum setting</title>
<updated>2020-06-02T18:50:23+00:00</updated>
<author>
<name>Daniel Borkmann</name>
<email>daniel@iogearbox.net</email>
</author>
<published>2020-06-02T14:58:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux.git/commit/?id=836e66c218f355ec01ba57671c85abf32961dcea'/>
<id>836e66c218f355ec01ba57671c85abf32961dcea</id>
<content type='text'>
Lorenz recently reported:

  In our TC classifier cls_redirect [0], we use the following sequence of
  helper calls to decapsulate a GUE (basically IP + UDP + custom header)
  encapsulated packet:

    bpf_skb_adjust_room(skb, -encap_len, BPF_ADJ_ROOM_MAC, BPF_F_ADJ_ROOM_FIXED_GSO)
    bpf_redirect(skb-&gt;ifindex, BPF_F_INGRESS)

  It seems like some checksums of the inner headers are not validated in
  this case. For example, a TCP SYN packet with invalid TCP checksum is
  still accepted by the network stack and elicits a SYN ACK. [...]

  That is, we receive the following packet from the driver:

    | ETH | IP | UDP | GUE | IP | TCP |
    skb-&gt;ip_summed == CHECKSUM_UNNECESSARY

  ip_summed is CHECKSUM_UNNECESSARY because our NICs do rx checksum offloading.
  On this packet we run skb_adjust_room_mac(-encap_len), and get the following:

    | ETH | IP | TCP |
    skb-&gt;ip_summed == CHECKSUM_UNNECESSARY

  Note that ip_summed is still CHECKSUM_UNNECESSARY. After bpf_redirect()'ing
  into the ingress, we end up in tcp_v4_rcv(). There, skb_checksum_init() is
  turned into a no-op due to CHECKSUM_UNNECESSARY.

The bpf_skb_adjust_room() helper is not aware of protocol specifics. Internally,
it handles the CHECKSUM_COMPLETE case via skb_postpull_rcsum(), but that does
not cover CHECKSUM_UNNECESSARY. In this case skb-&gt;csum_level of the original
skb prior to bpf_skb_adjust_room() call was 0, that is, covering UDP. Right now
there is no way to adjust the skb-&gt;csum_level. NICs that have checksum offload
disabled (CHECKSUM_NONE) or that support CHECKSUM_COMPLETE are not affected.

Use a safe default for CHECKSUM_UNNECESSARY by resetting to CHECKSUM_NONE and
add a flag to the helper called BPF_F_ADJ_ROOM_NO_CSUM_RESET that allows users
from opting out. Opting out is useful for the case where we don't remove/add
full protocol headers, or for the case where a user wants to adjust the csum
level manually e.g. through bpf_csum_level() helper that is added in subsequent
patch.

The bpf_skb_proto_{4_to_6,6_to_4}() for NAT64/46 translation from the BPF
bpf_skb_change_proto() helper uses bpf_skb_net_hdr_{push,pop}() pair internally
as well but doesn't change layers, only transitions between v4 to v6 and vice
versa, therefore no adoption is required there.

  [0] https://lore.kernel.org/bpf/20200424185556.7358-1-lmb@cloudflare.com/

Fixes: 2be7e212d541 ("bpf: add bpf_skb_adjust_room helper")
Reported-by: Lorenz Bauer &lt;lmb@cloudflare.com&gt;
Reported-by: Alan Maguire &lt;alan.maguire@oracle.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Signed-off-by: Lorenz Bauer &lt;lmb@cloudflare.com&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Reviewed-by: Alan Maguire &lt;alan.maguire@oracle.com&gt;
Link: https://lore.kernel.org/bpf/CACAyw9-uU_52esMd1JjuA80fRPHJv5vsSg8GnfW3t_qDU4aVKQ@mail.gmail.com/
Link: https://lore.kernel.org/bpf/11a90472e7cce83e76ddbfce81fdfce7bfc68808.1591108731.git.daniel@iogearbox.net
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Lorenz recently reported:

  In our TC classifier cls_redirect [0], we use the following sequence of
  helper calls to decapsulate a GUE (basically IP + UDP + custom header)
  encapsulated packet:

    bpf_skb_adjust_room(skb, -encap_len, BPF_ADJ_ROOM_MAC, BPF_F_ADJ_ROOM_FIXED_GSO)
    bpf_redirect(skb-&gt;ifindex, BPF_F_INGRESS)

  It seems like some checksums of the inner headers are not validated in
  this case. For example, a TCP SYN packet with invalid TCP checksum is
  still accepted by the network stack and elicits a SYN ACK. [...]

  That is, we receive the following packet from the driver:

    | ETH | IP | UDP | GUE | IP | TCP |
    skb-&gt;ip_summed == CHECKSUM_UNNECESSARY

  ip_summed is CHECKSUM_UNNECESSARY because our NICs do rx checksum offloading.
  On this packet we run skb_adjust_room_mac(-encap_len), and get the following:

    | ETH | IP | TCP |
    skb-&gt;ip_summed == CHECKSUM_UNNECESSARY

  Note that ip_summed is still CHECKSUM_UNNECESSARY. After bpf_redirect()'ing
  into the ingress, we end up in tcp_v4_rcv(). There, skb_checksum_init() is
  turned into a no-op due to CHECKSUM_UNNECESSARY.

The bpf_skb_adjust_room() helper is not aware of protocol specifics. Internally,
it handles the CHECKSUM_COMPLETE case via skb_postpull_rcsum(), but that does
not cover CHECKSUM_UNNECESSARY. In this case skb-&gt;csum_level of the original
skb prior to bpf_skb_adjust_room() call was 0, that is, covering UDP. Right now
there is no way to adjust the skb-&gt;csum_level. NICs that have checksum offload
disabled (CHECKSUM_NONE) or that support CHECKSUM_COMPLETE are not affected.

Use a safe default for CHECKSUM_UNNECESSARY by resetting to CHECKSUM_NONE and
add a flag to the helper called BPF_F_ADJ_ROOM_NO_CSUM_RESET that allows users
from opting out. Opting out is useful for the case where we don't remove/add
full protocol headers, or for the case where a user wants to adjust the csum
level manually e.g. through bpf_csum_level() helper that is added in subsequent
patch.

The bpf_skb_proto_{4_to_6,6_to_4}() for NAT64/46 translation from the BPF
bpf_skb_change_proto() helper uses bpf_skb_net_hdr_{push,pop}() pair internally
as well but doesn't change layers, only transitions between v4 to v6 and vice
versa, therefore no adoption is required there.

  [0] https://lore.kernel.org/bpf/20200424185556.7358-1-lmb@cloudflare.com/

Fixes: 2be7e212d541 ("bpf: add bpf_skb_adjust_room helper")
Reported-by: Lorenz Bauer &lt;lmb@cloudflare.com&gt;
Reported-by: Alan Maguire &lt;alan.maguire@oracle.com&gt;
Signed-off-by: Daniel Borkmann &lt;daniel@iogearbox.net&gt;
Signed-off-by: Lorenz Bauer &lt;lmb@cloudflare.com&gt;
Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Reviewed-by: Alan Maguire &lt;alan.maguire@oracle.com&gt;
Link: https://lore.kernel.org/bpf/CACAyw9-uU_52esMd1JjuA80fRPHJv5vsSg8GnfW3t_qDU4aVKQ@mail.gmail.com/
Link: https://lore.kernel.org/bpf/11a90472e7cce83e76ddbfce81fdfce7bfc68808.1591108731.git.daniel@iogearbox.net
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