@@ -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)
@@ -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,
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> --- Changes since v3: * also fix ipv6 Changes since v2: * rename l3_adj to net_adj * fix indentation Changes since v1: * introduce l3_adj to preserve the same returned value as before for tunnel mode For example: * on ipv4 with md5 AH and 3des ESP (transport mode): mtu = 1499 leads to FRAGFAILS mtu = 1500 the addition of padding in the esp header could be avoided * on ipv6 with md5 AH and twofish-sha1 ESP (transport mode): mtu = 1491 leads to Ip6FragFails mtu = 1499 padding can be avoided For details on how the formula is established, see https://lkml.org/lkml/2012/5/10/597 Tested with * transport mode E * transport mode EA * transport mode E + ah * tunnel mode E Not tested with BEET, but it should be the same as transport mode draft-nikander-esp-beet-mode-03.txt Section 5.2: "The wire packet format is identical to the ESP transport mode" --- net/ipv4/esp4.c | 24 +++++++++--------------- net/ipv6/esp6.c | 18 +++++++----------- 2 files changed, 16 insertions(+), 26 deletions(-)