[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>
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 5a00aa8..e144a25 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -279,7 +279,7 @@
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);
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index bdc65d8..a315d5d 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -272,32 +272,34 @@
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 @@
{
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 @@
}
}
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 @@
.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
};
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 6b76c4c..7107bb7 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -235,22 +235,24 @@
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 @@
.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,
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 63a20e8..69a3600 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1667,37 +1667,17 @@
}
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;
+ int res;
- 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);
- }
-
+ 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;
}