From f41f72d09ee1e9a980a1675be31120f547f2a648 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Thu, 31 Oct 2019 15:51:21 +0100 Subject: [PATCH] netfilter: nft_payload: simplify vlan header handling If the offset is within the ethernet + vlan header size boundary, then rebuild the ethernet + vlan header and use it to copy the bytes to the register. Otherwise, subtract the vlan header size from the offset and fall back to use skb_copy_bits(). There is one corner case though: If the offset plus the length of the payload instruction goes over the ethernet + vlan header boundary, then, fetch as many bytes as possible from the rebuilt ethernet + vlan header and fall back to copy the remaining bytes through skb_copy_bits(). Signed-off-by: Pablo Neira Ayuso Acked-by: Florian Westphal --- net/netfilter/nft_payload.c | 28 +++++++++------------------- 1 file changed, 9 insertions(+), 19 deletions(-) diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c index 5cb2d89..2477998 100644 --- a/net/netfilter/nft_payload.c +++ b/net/netfilter/nft_payload.c @@ -28,17 +28,22 @@ static bool nft_payload_copy_vlan(u32 *d, const struct sk_buff *skb, u8 offset, u8 len) { int mac_off = skb_mac_header(skb) - skb->data; - u8 vlan_len, *vlanh, *dst_u8 = (u8 *) d; + u8 *vlanh, *dst_u8 = (u8 *) d; struct vlan_ethhdr veth; vlanh = (u8 *) &veth; - if (offset < ETH_HLEN) { - u8 ethlen = min_t(u8, len, ETH_HLEN - offset); + if (offset < VLAN_ETH_HLEN) { + u8 ethlen = len; if (skb_copy_bits(skb, mac_off, &veth, ETH_HLEN)) return false; veth.h_vlan_proto = skb->vlan_proto; + veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb)); + veth.h_vlan_encapsulated_proto = skb->protocol; + + if (offset + len > VLAN_ETH_HLEN) + ethlen -= offset + len - VLAN_ETH_HLEN; memcpy(dst_u8, vlanh + offset, ethlen); @@ -48,25 +53,10 @@ nft_payload_copy_vlan(u32 *d, const struct sk_buff *skb, u8 offset, u8 len) dst_u8 += ethlen; offset = ETH_HLEN; - } else if (offset >= VLAN_ETH_HLEN) { + } else { offset -= VLAN_HLEN; - goto skip; } - veth.h_vlan_TCI = htons(skb_vlan_tag_get(skb)); - veth.h_vlan_encapsulated_proto = skb->protocol; - - vlanh += offset; - - vlan_len = min_t(u8, len, VLAN_ETH_HLEN - offset); - memcpy(dst_u8, vlanh, vlan_len); - - len -= vlan_len; - if (!len) - return true; - - dst_u8 += vlan_len; - skip: return skb_copy_bits(skb, offset + mac_off, dst_u8, len) == 0; } -- 2.7.4