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net: create skb_gso_validate_mac_len()

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If you take a GSO skb, and split it into packets, will the MAC
length (L2 + L3 + L4 headers + payload) of those packets be small
enough to fit within a given length?

Move skb_gso_mac_seglen() to skbuff.h with other related functions
like skb_gso_network_seglen() so we can use it, and then create
skb_gso_validate_mac_len to do the full calculation.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Axtens 2018-01-31 14:15:33 +11:00 committed by David S. Miller
parent 255442c938
commit 2b16f04872
3 changed files with 71 additions and 28 deletions
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16
include/linux/skbuff.h
View File

@ -3287,6 +3287,7 @@ 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);
bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len);
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);
@ -4120,6 +4121,21 @@ static inline unsigned int skb_gso_network_seglen(const struct sk_buff *skb)
return hdr_len + skb_gso_transport_seglen(skb);
}
/**
* skb_gso_mac_seglen - Return length of individual segments of a gso packet
*
* @skb: GSO skb
*
* skb_gso_mac_seglen is used to determine the real size of the
* individual segments, including MAC/L2, Layer3 (IP, IPv6) and L4
* headers (TCP/UDP).
*/
static inline unsigned int skb_gso_mac_seglen(const struct sk_buff *skb)
{
unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
return hdr_len + skb_gso_transport_seglen(skb);
}
/* Local Checksum Offload.
* Compute outer checksum based on the assumption that the
* inner checksum will be offloaded later.

73
net/core/skbuff.c
View File

@ -4913,6 +4913,45 @@ unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
}
EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
/**
* skb_gso_size_check - check the skb size, considering GSO_BY_FRAGS
*
* There are a couple of instances where we have a GSO skb, and we
* want to determine what size it would be after it is segmented.
*
* We might want to check:
* - L3+L4+payload size (e.g. IP forwarding)
* - L2+L3+L4+payload size (e.g. sanity check before passing to driver)
*
* This is a helper to do that correctly considering GSO_BY_FRAGS.
*
* @seg_len: The segmented length (from skb_gso_*_seglen). In the
* GSO_BY_FRAGS case this will be [header sizes + GSO_BY_FRAGS].
*
* @max_len: The maximum permissible length.
*
* Returns true if the segmented length <= max length.
*/
static inline bool skb_gso_size_check(const struct sk_buff *skb,
unsigned int seg_len,
unsigned int max_len) {
const struct skb_shared_info *shinfo = skb_shinfo(skb);
const struct sk_buff *iter;
if (shinfo->gso_size != GSO_BY_FRAGS)
return seg_len <= max_len;
/* Undo this so we can re-use header sizes */
seg_len -= GSO_BY_FRAGS;
skb_walk_frags(skb, iter) {
if (seg_len + skb_headlen(iter) > max_len)
return false;
}
return true;
}
/**
* skb_gso_validate_mtu - Return in case such skb fits a given MTU
*
@ -4924,27 +4963,25 @@ EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);
*/
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;
skb_walk_frags(skb, iter) {
if (hlen + skb_headlen(iter) > mtu)
return false;
}
return true;
return skb_gso_size_check(skb, skb_gso_network_seglen(skb), mtu);
}
EXPORT_SYMBOL_GPL(skb_gso_validate_mtu);
/**
* skb_gso_validate_mac_len - Will a split GSO skb fit in a given length?
*
* @skb: GSO skb
* @len: length to validate against
*
* skb_gso_validate_mac_len validates if a given skb will fit a wanted
* length once split, including L2, L3 and L4 headers and the payload.
*/
bool skb_gso_validate_mac_len(const struct sk_buff *skb, unsigned int len)
{
return skb_gso_size_check(skb, skb_gso_mac_seglen(skb), len);
}
EXPORT_SYMBOL_GPL(skb_gso_validate_mac_len);
static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
{
if (skb_cow(skb, skb_headroom(skb)) < 0) {

10
net/sched/sch_tbf.c
View File

@ -142,16 +142,6 @@ static u64 psched_ns_t2l(const struct psched_ratecfg *r,
return len;
}
/*
* Return length of individual segments of a gso packet,
* including all headers (MAC, IP, TCP/UDP)
*/
static unsigned int skb_gso_mac_seglen(const struct sk_buff *skb)
{
unsigned int hdr_len = skb_transport_header(skb) - skb_mac_header(skb);
return hdr_len + skb_gso_transport_seglen(skb);
}
/* GSO packet is too big, segment it so that tbf can transmit
* each segment in time
*/