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Commit ae7ef81e authored by Marcelo Ricardo Leitner's avatar Marcelo Ricardo Leitner Committed by David S. Miller
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skbuff: introduce skb_gso_validate_mtu 



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: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: default avatarXin Long <lucien.xin@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3953c46c

include/linux/skbuff.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

net/core/skbuff.c

+31 −0
Original line number Diff line number Diff line
@@ -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;



	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) {

net/ipv4/ip_forward.c

+1 −1
Original line number Diff line number Diff line
@@ -54,7 +54,7 @@ static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu) 
	if (skb->ignore_df)

		return false;



	if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)

	if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))

		return false;



	return true;

net/ipv4/ip_output.c

+1 −1
Original line number Diff line number Diff line
@@ -225,7 +225,7 @@ static int ip_finish_output_gso(struct net *net, struct sock *sk, 


	/* common case: locally created skb or seglen is <= mtu */

	if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||

	      skb_gso_network_seglen(skb) <= mtu)

	      skb_gso_validate_mtu(skb, mtu))

		return ip_finish_output2(net, sk, skb);



	/* Slowpath -  GSO segment length is exceeding the dst MTU.

net/ipv6/ip6_output.c

+1 −1
Original line number Diff line number Diff line
@@ -368,7 +368,7 @@ static bool ip6_pkt_too_big(const struct sk_buff *skb, unsigned int mtu) 
	if (skb->ignore_df)

		return false;



	if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu)

	if (skb_is_gso(skb) && skb_gso_validate_mtu(skb, mtu))

		return false;



	return true;