From c5c2523893747f88a83376abad310c8ad13f7197 Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Mon, 9 Apr 2007 11:47:18 -0700 Subject: [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 Signed-off-by: David S. Miller --- net/xfrm/xfrm_state.c | 36 ++++++++---------------------------- 1 file changed, 8 insertions(+), 28 deletions(-) (limited to 'net/xfrm') 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; } -- cgit v1.2.3