[ 74/82] xfrm: take net hdr len into account for esp payload size calculation

Ben Hutchings
2012-06-08T05:12:54Z

From: Benjamin Poirier <bpoirier@suse.de>

[ Upstream commit 91657eafb64b4cb53ec3a2fbc4afc3497f735788 ]

Corrects the function that determines the esp payload size. The calculations
done in esp{4,6}_get_mtu() lead to overlength frames in transport mode for
certain mtu values and suboptimal frames for others.

According to what is done, mainly in esp{,6}_output() and tcp_mtu_to_mss(),
net_header_len must be taken into account before doing the alignment
calculation.

Signed-off-by: Benjamin Poirier <bpoirier@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv4/esp4.c | 24 +++++++++---------------
net/ipv6/esp6.c | 18 +++++++-----------
2 files changed, 16 insertions(+), 26 deletions(-)

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index a5b4134..530787b 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -457,28 +457,22 @@ static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)
struct esp_data *esp = x->data;
u32 blksize = ALIGN(crypto_aead_blocksize(esp->aead), 4);
u32 align = max_t(u32, blksize, esp->padlen);
- u32 rem;
-
- mtu -= x->props.header_len + crypto_aead_authsize(esp->aead);
- rem = mtu & (align - 1);
- mtu &= ~(align - 1);
+ unsigned int net_adj;

switch (x->props.mode) {
- case XFRM_MODE_TUNNEL:
- break;
- default:
case XFRM_MODE_TRANSPORT:
- /* The worst case */
- mtu -= blksize - 4;
- mtu += min_t(u32, blksize - 4, rem);
- break;
case XFRM_MODE_BEET:
- /* The worst case. */
- mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);
+ net_adj = sizeof(struct iphdr);
break;
+ case XFRM_MODE_TUNNEL:
+ net_adj = 0;
+ break;
+ default:
+ BUG();
}

- return mtu - 2;
+ return ((mtu - x->props.header_len - crypto_aead_authsize(esp->aead) -
+ net_adj) & ~(align - 1)) + (net_adj - 2);
}

static void esp4_err(struct sk_buff *skb, u32 info)
diff --git a/net/ipv6/esp6.c b/net/ipv6/esp6.c
index 1ac7938..65dd543 100644
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -411,19 +411,15 @@ static u32 esp6_get_mtu(struct xfrm_state *x, int mtu)
struct esp_data *esp = x->data;
u32 blksize = ALIGN(crypto_aead_blocksize(esp->aead), 4);
u32 align = max_t(u32, blksize, esp->padlen);
- u32 rem;
+ unsigned int net_adj;

- mtu -= x->props.header_len + crypto_aead_authsize(esp->aead);
- rem = mtu & (align - 1);
- mtu &= ~(align - 1);
-
- if (x->props.mode != XFRM_MODE_TUNNEL) {
- u32 padsize = ((blksize - 1) & 7) + 1;
- mtu -= blksize - padsize;
- mtu += min_t(u32, blksize - padsize, rem);
- }
+ if (x->props.mode != XFRM_MODE_TUNNEL)
+ net_adj = sizeof(struct ipv6hdr);
+ else
+ net_adj = 0;

- return mtu - 2;
+ return ((mtu - x->props.header_len - crypto_aead_authsize(esp->aead) -
+ net_adj) & ~(align - 1)) + (net_adj - 2);
}

static void esp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,