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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
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30
net/ipv4/esp4.c
View File

@@ -272,32 +272,34 @@ out:
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
};