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authorMartin Willi <martin@strongswan.org>2010-12-08 04:37:50 +0000
committerDavid S. Miller <davem@davemloft.net>2010-12-10 14:43:59 -0800
commitd979e20f2b9f8a50c8d5f889e0b5d78580440d1f (patch)
treefed3b0c657cfb62d0e2f3df25fbc4cad058059b2 /net
parent35d2856b4693e8de5d616307b56cef296b839157 (diff)
xfrm: Traffic Flow Confidentiality for IPv4 ESP
Add TFC padding to all packets smaller than the boundary configured on the xfrm state. If the boundary is larger than the PMTU, limit padding to the PMTU. Signed-off-by: Martin Willi <martin@strongswan.org> Acked-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/esp4.c32
1 files changed, 24 insertions, 8 deletions
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 14ca1f1c3fb0..e42a905180f0 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -23,6 +23,8 @@ struct esp_skb_cb {
#define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))
+static u32 esp4_get_mtu(struct xfrm_state *x, int mtu);
+
/*
* Allocate an AEAD request structure with extra space for SG and IV.
*
@@ -117,25 +119,35 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
int blksize;
int clen;
int alen;
+ int plen;
+ int tfclen;
int nfrags;
/* skb is pure payload to encrypt */
err = -ENOMEM;
- /* Round to block size */
- clen = skb->len;
-
esp = x->data;
aead = esp->aead;
alen = crypto_aead_authsize(aead);
+ tfclen = 0;
+ if (x->tfcpad) {
+ struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
+ u32 padto;
+
+ padto = min(x->tfcpad, esp4_get_mtu(x, dst->child_mtu_cached));
+ if (skb->len < padto)
+ tfclen = padto - skb->len;
+ }
blksize = ALIGN(crypto_aead_blocksize(aead), 4);
- clen = ALIGN(clen + 2, blksize);
+ clen = ALIGN(skb->len + 2 + tfclen, blksize);
if (esp->padlen)
clen = ALIGN(clen, esp->padlen);
+ plen = clen - skb->len - tfclen;
- if ((err = skb_cow_data(skb, clen - skb->len + alen, &trailer)) < 0)
+ err = skb_cow_data(skb, tfclen + plen + alen, &trailer);
+ if (err < 0)
goto error;
nfrags = err;
@@ -150,13 +162,17 @@ static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
/* Fill padding... */
tail = skb_tail_pointer(trailer);
+ if (tfclen) {
+ memset(tail, 0, tfclen);
+ tail += tfclen;
+ }
do {
int i;
- for (i=0; i<clen-skb->len - 2; i++)
+ for (i = 0; i < plen - 2; i++)
tail[i] = i + 1;
} while (0);
- tail[clen - skb->len - 2] = (clen - skb->len) - 2;
- tail[clen - skb->len - 1] = *skb_mac_header(skb);
+ tail[plen - 2] = plen - 2;
+ tail[plen - 1] = *skb_mac_header(skb);
pskb_put(skb, trailer, clen - skb->len + alen);
skb_push(skb, -skb_network_offset(skb));