前段時間我實現了基於vinat模塊的Ashbash Kashyap(http://www.research.rutgers.edu/~ashwink/misc_projs/ebt_vnat.html)的ebtables模塊。模塊可用於佈線表中的BROUTING鏈,用於剝離vlan標籤並將vlan id置於nf標記中。模塊還允許在nat表的POSTROUTING鏈中添加基於nf標記值的vlan標記。模塊在處理橋接通信時沒有任何問題。系統堅如磐石。一旦將tproxy截取添加到混音中,問題就會開始。這會在操作一段時間後導致內核恐慌。我強調這一事實,即在幾分鐘的流量流之後的第一個數據包之後,我看不到內核崩潰。看起來,我修理SKB的方式對L3 +處理來說不夠乾淨。順便說一句我正在研究2.6.32內核。 (只要他們有至少64位長)定製ebtables模塊&& skb操作&& kernel panic
// code for adding vlan tag based on skb->mark value
if (!skb_make_writable(skb, 0))
return EBT_DROP;
if(skb->mark > 0){
// maybe we should always seek VLAN_HLEN+ETH_HLEN instead of using condition?
if (skb_headroom(skb) < (skb->mac_len == 0 ? VLAN_HLEN + ETH_HLEN : VLAN_HLEN)) {
struct sk_buff *sk_tmp = skb;
skb = skb_realloc_headroom(sk_tmp, VLAN_HLEN);
kfree_skb(sk_tmp);
if (skb == NULL) {
return EBT_DROP;
}
}
// we need 4 more bytes for 802.1q header, so push!...I can almost see the head(er)
skb_push(skb, VLAN_HLEN);
skb->mac_header-=VLAN_HLEN;
skb->network_header-=VLAN_HLEN;
skb->transport_header-=VLAN_HLEN;
veth = (struct vlan_ethhdr *) eth_hdr(skb);
// move dst/src mac addresses (12b of header) 4 bytes back to make room for
// 802.1q header
memmove(skb->head + skb->mac_header, skb->head + skb->mac_header + VLAN_HLEN, 12);
// fill 802.1q header
veth->h_vlan_proto = __constant_htons(ETH_P_8021Q);
veth_TCI = skb->mark & 0xfff;
veth->h_vlan_TCI = htons(veth_TCI);
}
// code for stripping vlan tag and putting it into skb->mark value
veth = (struct vlan_ethhdr *)eth_hdr(skb);
if(veth->h_vlan_proto == __constant_htons(ETH_P_8021Q)){
if (!skb_make_writable(skb, 0))
return EBT_DROP;
// determine vlan id
vid=(ntohs(veth->h_vlan_TCI) & 0xfff);
mark = vid;
// copy dst/src mac addresses (12b) 4 bytes fwd, so it covers 802.1q header
memmove(skb->head + skb->mac_header + VLAN_HLEN, skb->head + skb->mac_header, 12);
// adapt header pointers
skb->mac_header+=VLAN_HLEN;
skb->mac_len = ETH_HLEN;
skb->network_header+=VLAN_HLEN;
skb->transport_header+=VLAN_HLEN;
skb->data += VLAN_HLEN;
skb->len -= VLAN_HLEN;
eth = eth_hdr(skb);
skb->protocol=eth->h_proto;
}
skb->mark=mark;
我會爲任何指針感激:請找到該模塊的關鍵部分與下面的評論。謝謝!