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| author | Sowmini Varadhan <sowmini.varadhan@oracle.com> | 2016-04-23 04:36:35 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-04-25 23:54:14 +0300 |
| commit | 6fa01ccd883021105e9f8af7d04b9f156fa3494a (patch) | |
| tree | bb3715e5d0e662ee1e9d285c15033bd7ea5da40c /include/linux/skbuff.h | |
| parent | 557fc4a098039cf296fe33f118bab99a925fd881 (diff) | |
| download | linux-6fa01ccd883021105e9f8af7d04b9f156fa3494a.tar.xz | |
skbuff: Add pskb_extract() helper function
A pattern of skb usage seen in modules such as RDS-TCP is to
extract `to_copy' bytes from the received TCP segment, starting
at some offset `off' into a new skb `clone'. This is done in
the ->data_ready callback, where the clone skb is queued up for rx on
the PF_RDS socket, while the parent TCP segment is returned unchanged
back to the TCP engine.
The existing code uses the sequence
clone = skb_clone(..);
pskb_pull(clone, off, ..);
pskb_trim(clone, to_copy, ..);
with the intention of discarding the first `off' bytes. However,
skb_clone() + pskb_pull() implies pksb_expand_head(), which ends
up doing a redundant memcpy of bytes that will then get discarded
in __pskb_pull_tail().
To avoid this inefficiency, this commit adds pskb_extract() that
creates the clone, and memcpy's only the relevant header/frag/frag_list
to the start of `clone'. pskb_trim() is then invoked to trim clone
down to the requested to_copy bytes.
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/skbuff.h')
| -rw-r--r-- | include/linux/skbuff.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index da0ace389fec..a1ce63979ad8 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2986,6 +2986,8 @@ struct sk_buff *skb_vlan_untag(struct sk_buff *skb); int skb_ensure_writable(struct sk_buff *skb, int write_len); int skb_vlan_pop(struct sk_buff *skb); int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci); +struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy, + gfp_t gfp); static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len) { |