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Date:   Mon, 2 Aug 2021 11:52:08 +0300
From:   Vasily Averin <>
To:     "David S. Miller" <>,
        Hideaki YOSHIFUJI <>,
        David Ahern <>,
        Jakub Kicinski <>,
        Eric Dumazet <>
Cc:, Joerg Reuter <>,
        Ralf Baechle <>,,
        Alexei Starovoitov <>,
        Daniel Borkmann <>,
        Andrii Nakryiko <>,
        Martin KaFai Lau <>,
        Song Liu <>, Yonghong Song <>,
        KP Singh <>,,
Subject: [PATCH NET v3 0/7] skbuff: introduce skb_expand_head()

currently if skb does not have enough headroom skb_realloc_headrom is called.
It is not optimal because it creates new skb.

this patch set introduces new helper skb_expand_head()
Unlike skb_realloc_headroom, it does not allocate a new skb if possible; 
copies skb->sk on new skb when as needed and frees original skb in case of failures.

This helps to simplify ip[6]_finish_output2(), ip6_xmit() and few other
functions in vrf, ax25 and bpf.

There are few other cases where this helper can be used 
but it requires an additional investigations. 

v3 changes:
 - ax25 compilation warning fixed
 - v5.14-rc4 rebase
 - now it does not depend on non-committed pathces

v2 changes:
 - helper's name was changed to skb_expand_head
 - fixed few mistakes inside skb_expand_head():
    skb_set_owner_w should set sk on nskb
    kfree was replaced by kfree_skb()
    improved warning message
 - added minor refactoring in changed functions in vrf and bpf patches
 - removed kfree_skb() in ax25_rt_build_path caller ax25_ip_xmit

Vasily Averin (7):
  skbuff: introduce skb_expand_head()
  ipv6: use skb_expand_head in ip6_finish_output2
  ipv6: use skb_expand_head in ip6_xmit
  ipv4: use skb_expand_head in ip_finish_output2
  vrf: use skb_expand_head in vrf_finish_output
  ax25: use skb_expand_head
  bpf: use skb_expand_head in bpf_out_neigh_v4/6

 drivers/net/vrf.c      | 21 +++++---------
 include/linux/skbuff.h |  1 +
 net/ax25/ax25_ip.c     |  4 +--
 net/ax25/ax25_out.c    | 13 ++-------
 net/ax25/ax25_route.c  | 13 ++-------
 net/core/filter.c      | 27 ++++-------------
 net/core/skbuff.c      | 42 +++++++++++++++++++++++++++
 net/ipv4/ip_output.c   | 13 ++-------
 net/ipv6/ip6_output.c  | 78 +++++++++++++++++---------------------------------
 9 files changed, 91 insertions(+), 121 deletions(-)


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