Commit 2b16f048 authored by Daniel Axtens's avatar Daniel Axtens Committed by David S. Miller
Browse files

net: create skb_gso_validate_mac_len() 



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: default avatarDaniel Axtens <dja@axtens.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 255442c9

include/linux/skbuff.h

+16 −0
Original line number Diff line number Diff line
@@ -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.

net/core/skbuff.c

+50 −13
Original line number Diff line number Diff line
@@ -4914,37 +4914,74 @@ 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_size_check - check the skb size, considering GSO_BY_FRAGS

 *

 * @skb: GSO skb

 * @mtu: MTU to validate against

 * 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.

 *

 * skb_gso_validate_mtu validates if a given skb will fit a wanted MTU

 * once split.

 * 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.

 */

bool skb_gso_validate_mtu(const struct sk_buff *skb, unsigned int mtu)

{

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;

	unsigned int hlen;



	hlen = skb_gso_network_seglen(skb);



	if (shinfo->gso_size != GSO_BY_FRAGS)

		return hlen <= mtu;

		return seg_len <= max_len;



	/* Undo this so we can re-use header sizes */

	hlen -= GSO_BY_FRAGS;

	seg_len -= GSO_BY_FRAGS;



	skb_walk_frags(skb, iter) {

		if (hlen + skb_headlen(iter) > mtu)

		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

 *

 * @skb: GSO skb

 * @mtu: MTU to validate against

 *

 * 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)

{

	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) {

net/sched/sch_tbf.c

+0 −10
Original line number Diff line number Diff line
@@ -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

 */

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