xfrm: take net hdr len into account for esp payload size calculation

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>

diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index 89a47b3..cb982a6 100644 (file)
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -459,28 +459,22 @@ 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 1e62b75..db1521f 100644 (file)
--- a/net/ipv6/esp6.c
+++ b/net/ipv6/esp6.c
@@ -413,19 +413,15 @@ 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,