Commit 07e1d6b3 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'skb_expand_head' 



Vasily Averin says:

====================
skbuff: introduce skb_expand_head()

currently if skb does not have enough headroom skb_realloc_headrom is called.
It is not optimal because it creates new skb.

this patch set introduces new helper skb_expand_head()
Unlike skb_realloc_headroom, it does not allocate a new skb if possible;
copies skb->sk on new skb when as needed and frees original skb in case of failures.

This helps to simplify ip[6]_finish_output2(), ip6_xmit() and few other
functions in vrf, ax25 and bpf.

There are few other cases where this helper can be used
but it requires an additional investigations.

v3 changes:
 - ax25 compilation warning fixed
 - v5.14-rc4 rebase
 - now it does not depend on non-committed pathces

v2 changes:
 - helper's name was changed to skb_expand_head
 - fixed few mistakes inside skb_expand_head():
    skb_set_owner_w should set sk on nskb
    kfree was replaced by kfree_skb()
    improved warning message
 - added minor refactoring in changed functions in vrf and bpf patches
 - removed kfree_skb() in ax25_rt_build_path caller ax25_ip_xmit
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents fa976624 a1e975e1

drivers/net/vrf.c

+7 −14
Original line number Diff line number Diff line
@@ -857,30 +857,24 @@ static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *s 
	unsigned int hh_len = LL_RESERVED_SPACE(dev);

	struct neighbour *neigh;

	bool is_v6gw = false;

	int ret = -EINVAL;



	nf_reset_ct(skb);



	/* Be paranoid, rather than too clever. */

	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {

		struct sk_buff *skb2;



		skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));

		if (!skb2) {

			ret = -ENOMEM;

			goto err;

		skb = skb_expand_head(skb, hh_len);

		if (!skb) {

			skb->dev->stats.tx_errors++;

			return -ENOMEM;

		}

		if (skb->sk)

			skb_set_owner_w(skb2, skb->sk);



		consume_skb(skb);

		skb = skb2;

	}



	rcu_read_lock_bh();



	neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);

	if (!IS_ERR(neigh)) {

		int ret;



		sock_confirm_neigh(skb, neigh);

		/* if crossing protocols, can not use the cached header */

		ret = neigh_output(neigh, skb, is_v6gw);
@@ -889,9 +883,8 @@ static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *s 
	}



	rcu_read_unlock_bh();

err:

	vrf_tx_error(skb->dev, skb);

	return ret;

	return -EINVAL;

}



static int vrf_output(struct net *net, struct sock *sk, struct sk_buff *skb)

include/linux/skbuff.h

+1 −0
Original line number Diff line number Diff line
@@ -1183,6 +1183,7 @@ static inline struct sk_buff *__pskb_copy(struct sk_buff *skb, int headroom, 
int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, gfp_t gfp_mask);

struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,

				     unsigned int headroom);

struct sk_buff *skb_expand_head(struct sk_buff *skb, unsigned int headroom);

struct sk_buff *skb_copy_expand(const struct sk_buff *skb, int newheadroom,

				int newtailroom, gfp_t priority);

int __must_check skb_to_sgvec_nomark(struct sk_buff *skb, struct scatterlist *sg,

net/ax25/ax25_ip.c

+1 −3
Original line number Diff line number Diff line
@@ -193,10 +193,8 @@ netdev_tx_t ax25_ip_xmit(struct sk_buff *skb) 
	skb_pull(skb, AX25_KISS_HEADER_LEN);



	if (digipeat != NULL) {

		if ((ourskb = ax25_rt_build_path(skb, src, dst, route->digipeat)) == NULL) {

			kfree_skb(skb);

		if ((ourskb = ax25_rt_build_path(skb, src, dst, route->digipeat)) == NULL)

			goto put;

		}



		skb = ourskb;

	}

net/ax25/ax25_out.c

+3 −10
Original line number Diff line number Diff line
@@ -325,7 +325,6 @@ void ax25_kick(ax25_cb *ax25) 


void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)

{

	struct sk_buff *skbn;

	unsigned char *ptr;

	int headroom;
@@ -336,18 +335,12 @@ void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type) 


	headroom = ax25_addr_size(ax25->digipeat);



	if (skb_headroom(skb) < headroom) {

		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {

	if (unlikely(skb_headroom(skb) < headroom)) {

		skb = skb_expand_head(skb, headroom);

		if (!skb) {

			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");

			kfree_skb(skb);

			return;

		}



		if (skb->sk != NULL)

			skb_set_owner_w(skbn, skb->sk);



		consume_skb(skb);

		skb = skbn;

	}



	ptr = skb_push(skb, headroom);

net/ax25/ax25_route.c

+3 −10
Original line number Diff line number Diff line
@@ -441,24 +441,17 @@ int ax25_rt_autobind(ax25_cb *ax25, ax25_address *addr) 
struct sk_buff *ax25_rt_build_path(struct sk_buff *skb, ax25_address *src,

	ax25_address *dest, ax25_digi *digi)

{

	struct sk_buff *skbn;

	unsigned char *bp;

	int len;



	len = digi->ndigi * AX25_ADDR_LEN;



	if (skb_headroom(skb) < len) {

		if ((skbn = skb_realloc_headroom(skb, len)) == NULL) {

	if (unlikely(skb_headroom(skb) < len)) {

		skb = skb_expand_head(skb, len);

		if (!skb) {

			printk(KERN_CRIT "AX.25: ax25_dg_build_path - out of memory\n");

			return NULL;

		}



		if (skb->sk != NULL)

			skb_set_owner_w(skbn, skb->sk);



		consume_skb(skb);



		skb = skbn;

	}



	bp = skb_push(skb, len);