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[XFRM]: Optimize MTU calculation

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Replace the probing based MTU estimation, which usually takes 2-3 iterations
to find a fitting value and may underestimate the MTU, by an exact calculation.

Also fix underestimation of the XFRM trailer_len, which causes unnecessary
reallocations.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy 2007-04-09 11:47:18 -07:00 committed by David S. Miller
parent 557922584d
commit c5c2523893
4 changed files with 39 additions and 51 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/xfrm.h
View File

@ -279,7 +279,7 @@ struct xfrm_type
xfrm_address_t *(*local_addr)(struct xfrm_state *, xfrm_address_t *);
xfrm_address_t *(*remote_addr)(struct xfrm_state *, xfrm_address_t *);
/* Estimate maximal size of result of transformation of a dgram */
u32 (*get_max_size)(struct xfrm_state *, int size);
u32 (*get_mtu)(struct xfrm_state *, int size);
};
extern int xfrm_register_type(struct xfrm_type *type, unsigned short family);

30
net/ipv4/esp4.c
View File

@ -272,32 +272,34 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
return -EINVAL;
}
static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
{
struct esp_data *esp = x->data;
u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
int enclen = 0;
u32 align = max_t(u32, blksize, esp->conf.padlen);
u32 rem;
mtu -= x->props.header_len + esp->auth.icv_trunc_len;
rem = mtu & (align - 1);
mtu &= ~(align - 1);
switch (x->props.mode) {
case XFRM_MODE_TUNNEL:
mtu = ALIGN(mtu +2, blksize);
break;
default:
case XFRM_MODE_TRANSPORT:
/* The worst case */
mtu = ALIGN(mtu + 2, 4) + blksize - 4;
mtu -= blksize - 4;
mtu += min_t(u32, blksize - 4, rem);
break;
case XFRM_MODE_BEET:
/* The worst case. */
enclen = IPV4_BEET_PHMAXLEN;
mtu = ALIGN(mtu + enclen + 2, blksize);
mtu -= IPV4_BEET_PHMAXLEN;
mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
break;
}
if (esp->conf.padlen)
mtu = ALIGN(mtu, esp->conf.padlen);
return mtu + x->props.header_len + esp->auth.icv_trunc_len - enclen;
return mtu - 2;
}
static void esp4_err(struct sk_buff *skb, u32 info)
@ -340,6 +342,7 @@ static int esp_init_state(struct xfrm_state *x)
{
struct esp_data *esp = NULL;
struct crypto_blkcipher *tfm;
u32 align;
/* null auth and encryption can have zero length keys */
if (x->aalg) {
@ -421,7 +424,10 @@ static int esp_init_state(struct xfrm_state *x)
}
}
x->data = esp;
x->props.trailer_len = esp4_get_max_size(x, 0) - x->props.header_len;
align = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
if (esp->conf.padlen)
align = max_t(u32, align, esp->conf.padlen);
x->props.trailer_len = align + 1 + esp->auth.icv_trunc_len;
return 0;
error:
@ -438,7 +444,7 @@ static struct xfrm_type esp_type =
.proto = IPPROTO_ESP,
.init_state = esp_init_state,
.destructor = esp_destroy,
.get_max_size = esp4_get_max_size,
.get_mtu = esp4_get_mtu,
.input = esp_input,
.output = esp_output
};

22
net/ipv6/esp6.c
View File

@ -235,22 +235,24 @@ static int esp6_input(struct xfrm_state *x, struct sk_buff *skb)
return ret;
}
static u32 esp6_get_max_size(struct xfrm_state *x, int mtu)
static u32 esp6_get_mtu(struct xfrm_state *x, int mtu)
{
struct esp_data *esp = x->data;
u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
u32 align = max_t(u32, blksize, esp->conf.padlen);
u32 rem;
if (x->props.mode == XFRM_MODE_TUNNEL) {
mtu = ALIGN(mtu + 2, blksize);
} else {
/* The worst case. */
mtu -= x->props.header_len + esp->auth.icv_trunc_len;
rem = mtu & (align - 1);
mtu &= ~(align - 1);
if (x->props.mode != XFRM_MODE_TUNNEL) {
u32 padsize = ((blksize - 1) & 7) + 1;
mtu = ALIGN(mtu + 2, padsize) + blksize - padsize;
mtu -= blksize - padsize;
mtu += min_t(u32, blksize - padsize, rem);
}
if (esp->conf.padlen)
mtu = ALIGN(mtu, esp->conf.padlen);
return mtu + x->props.header_len + esp->auth.icv_trunc_len;
return mtu - 2;
}
static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
@ -380,7 +382,7 @@ static struct xfrm_type esp6_type =
.proto = IPPROTO_ESP,
.init_state = esp6_init_state,
.destructor = esp6_destroy,
.get_max_size = esp6_get_max_size,
.get_mtu = esp6_get_mtu,
.input = esp6_input,
.output = esp6_output,
.hdr_offset = xfrm6_find_1stfragopt,

36
net/xfrm/xfrm_state.c
View File

@ -1667,37 +1667,17 @@ void xfrm_state_delete_tunnel(struct xfrm_state *x)
}
EXPORT_SYMBOL(xfrm_state_delete_tunnel);
/*
* This function is NOT optimal. For example, with ESP it will give an
* MTU that's usually two bytes short of being optimal. However, it will
* usually give an answer that's a multiple of 4 provided the input is
* also a multiple of 4.
*/
int xfrm_state_mtu(struct xfrm_state *x, int mtu)
{
int res = mtu;
res -= x->props.header_len;
for (;;) {
int m = res;
if (m < 68)
return 68;
spin_lock_bh(&x->lock);
if (x->km.state == XFRM_STATE_VALID &&
x->type && x->type->get_max_size)
m = x->type->get_max_size(x, m);
else
m += x->props.header_len;
spin_unlock_bh(&x->lock);
if (m <= mtu)
break;
res -= (m - mtu);
}
int res;
spin_lock_bh(&x->lock);
if (x->km.state == XFRM_STATE_VALID &&
x->type && x->type->get_mtu)
res = x->type->get_mtu(x, mtu);
else
res = mtu;
spin_unlock_bh(&x->lock);
return res;
}