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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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22
net/ipv6/esp6.c
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@ -235,22 +235,24 @@ out:
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,