From: Antonio Quartulli ordex@autistici.org
In case of a VLAN tagged frame the ethhdr pointer is moved forward by 4 bytes so that the offset of h_proto in struct ethhdr matches the real h_vlan_encapsulated_proto address in the skb. While this trickery is correct it makes the code harder to understand and may lead to bugs in case of re-use of ethhdr for other purposes.
This patch introduces a proto variable to make things cleaner and easier to understand.
Signed-off-by: Antonio Quartulli ordex@autistici.org Signed-off-by: Marek Lindner lindner_marek@yahoo.de --- net/batman-adv/gateway_client.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)
diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c index 1bce63a..ac97ca7 100644 --- a/net/batman-adv/gateway_client.c +++ b/net/batman-adv/gateway_client.c @@ -655,24 +655,29 @@ bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len) struct iphdr *iphdr; struct ipv6hdr *ipv6hdr; struct udphdr *udphdr; + struct vlan_ethhdr *vhdr; + __be16 proto;
/* check for ethernet header */ if (!pskb_may_pull(skb, *header_len + ETH_HLEN)) return false; ethhdr = (struct ethhdr *)skb->data; + proto = ethhdr->h_proto; *header_len += ETH_HLEN;
/* check for initial vlan header */ - if (ntohs(ethhdr->h_proto) == ETH_P_8021Q) { + if (proto == htons(ETH_P_8021Q)) { if (!pskb_may_pull(skb, *header_len + VLAN_HLEN)) return false; - ethhdr = (struct ethhdr *)(skb->data + VLAN_HLEN); + + vhdr = (struct vlan_ethhdr *)skb->data; + proto = vhdr->h_vlan_encapsulated_proto; *header_len += VLAN_HLEN; }
/* check for ip header */ - switch (ntohs(ethhdr->h_proto)) { - case ETH_P_IP: + switch (proto) { + case htons(ETH_P_IP): if (!pskb_may_pull(skb, *header_len + sizeof(*iphdr))) return false; iphdr = (struct iphdr *)(skb->data + *header_len); @@ -683,7 +688,7 @@ bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len) return false;
break; - case ETH_P_IPV6: + case htons(ETH_P_IPV6): if (!pskb_may_pull(skb, *header_len + sizeof(*ipv6hdr))) return false; ipv6hdr = (struct ipv6hdr *)(skb->data + *header_len); @@ -710,11 +715,11 @@ bool batadv_gw_is_dhcp_target(struct sk_buff *skb, unsigned int *header_len) *header_len += sizeof(*udphdr);
/* check for bootp port */ - if ((ntohs(ethhdr->h_proto) == ETH_P_IP) && + if ((proto == htons(ETH_P_IP)) && (ntohs(udphdr->dest) != 67)) return false;
- if ((ntohs(ethhdr->h_proto) == ETH_P_IPV6) && + if ((proto == htons(ETH_P_IPV6)) && (ntohs(udphdr->dest) != 547)) return false;