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authorPatrick McHardy <kaber@trash.net>2007-04-09 11:47:18 -0700
committerDavid S. Miller <davem@sunset.davemloft.net>2007-04-25 22:28:38 -0700
commitc5c2523893747f88a83376abad310c8ad13f7197 (patch)
tree58f1ab25ac9f7ca7460abbd24e9bab9c8683f6fd /net/xfrm
parent557922584d9c5b6b990bcfb2fec3134f0e73a05d (diff)
downloadlinux-c5c2523893747f88a83376abad310c8ad13f7197.tar.bz2
[XFRM]: Optimize MTU calculation
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>
Diffstat (limited to 'net/xfrm')
-rw-r--r--net/xfrm/xfrm_state.c36
1 files changed, 8 insertions, 28 deletions
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 63a20e818164..69a3600afd9d 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -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;
}