On Tue, May 31, 2016 at 11:55 AM, Marcelo Ricardo Leitner
<marcelo.leitner@xxxxxxxxx> wrote:
> skb_gso_network_seglen is not enough for checking fragment sizes if
> skb is using GSO_BY_FRAGS as we have to check frag per frag.
>
> This patch introduces skb_gso_validate_mtu, based on the former, which
> will wrap the use case inside it as all calls to skb_gso_network_seglen
> were to validate if it fits on a given TMU, and improve the check.
>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> Tested-by: Xin Long <lucien.xin@xxxxxxxxx>
> ---
> include/linux/skbuff.h | 1 +
> net/core/skbuff.c | 31 +++++++++++++++++++++++++++++++
> net/ipv4/ip_forward.c | 2 +-
> net/ipv4/ip_output.c | 2 +-
> net/ipv6/ip6_output.c | 2 +-
> net/mpls/af_mpls.c | 2 +-
> 6 files changed, 36 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 1f713541cb2fc232cb0e8417232cb9942409c9fc..2109c2dc9767d454b2cd08696af039b6bcd1ace7 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -2992,6 +2992,7 @@ void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
> int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
> void skb_scrub_packet(struct sk_buff *skb, bool xnet);
> unsigned int skb_gso_transport_seglen(const struct sk_buff *skb);
> +bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu);
> struct sk_buff *skb_segment(struct sk_buff *skb, netdev_features_t features);
> struct sk_buff *skb_vlan_untag(struct sk_buff *skb);
> int skb_ensure_writable(struct sk_buff *skb, int write_len);
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 97c32c75e704af1f31b064e8f1e0475ff1505d67..5ca562b56ec39d39e1225d96547e242732518ffe 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -4392,6 +4392,37 @@ unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
> }
> EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
>
> +/**
> + * skb_gso_validate_mtu - Return in case such skb fits a given MTU
> + *
> + * @skb: GSO skb
> + *
> + * skb_gso_validate_mtu validates if a given skb will fit a wanted MTU
> + * once split.
> + */
> +bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu)
> +{
> + const struct skb_shared_info *shinfo = skb_shinfo(skb);
> + const struct sk_buff *iter;
> + unsigned int hlen;
> +
> + hlen = skb_gso_network_seglen(skb);
> +
> + if (shinfo->gso_size != GSO_BY_FRAGS)
> + return hlen <= mtu;
> +
> + /* Undo this so we can re-use header sizes */
> + hlen -= GSO_BY_FRAGS;
Isn't this just "hlen = 0"? If so you could probably just remove this
line and the references to hlen below and instead just loop through
verifying skb_headlen() instead of adding a value that should be 0.
> + skb_walk_frags(skb, iter) {
> + if (hlen + skb_headlen(iter) > mtu)
> + return false;
> + }
> +
> + return true;
> +}
> +EXPORT_SYMBOL_GPL(skb_gso_validate_mtu);
> +
> static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
> {
> if (skb_cow(skb, skb_headroom(skb)) < 0) {
--
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