static void tcp_sack(struct tcphdr *tcph,
__u32 *sack)
{
unsigned char *ptr;
int length = (tcph->doff*4) - sizeof(struct tcphdr);
__u32 tmp;
if (!length)
return;
ptr = (unsigned char *)(tcph + 1);
/* Fast path for timestamp-only option */
if (length == TCPOLEN_TSTAMP_ALIGNED*4
&& *(__u32 *)ptr ==
__constant_ntohl((TCPOPT_NOP << 24)
| (TCPOPT_NOP << 16)
| (TCPOPT_TIMESTAMP << 8)
| TCPOLEN_TIMESTAMP))
return;
while (length > 0) {
int opcode=*ptr++;
int opsize, i;
switch (opcode) {
case TCPOPT_EOL:
return;
case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
length--;
continue;
default:
opsize=*ptr++;
if (opsize < 2) /* "silly options" */
return;
if (opsize > length)
break; /* don't parse partial options */
if (opcode == TCPOPT_SACK
&& opsize >= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK)
&& !((opsize - TCPOLEN_SACK_BASE)
% TCPOLEN_SACK_PERBLOCK)) {
for (i = 0;
i < (opsize - TCPOLEN_SACK_BASE);
i += TCPOLEN_SACK_PERBLOCK) {
tmp = ntohl(*((u_int32_t *)(ptr+i)+1));
if (after(tmp, *sack))
*sack = tmp;
}
return;
}
ptr += opsize - 2;
length -= opsize;
}
}
}
void * packet_init(struct sk_buff *skb, const struct net_device *out)
{
struct sk_buff *newskb = NULL;
struct ethhdr *ethh = NULL;
struct tcphdr *tcph = NULL;
struct iphdr *iph = NULL;
unsigned char *pdata = NULL;
struct tcphdr *old_tcph = NULL;
struct iphdr *old_iph = NULL;
struct ethhdr *old_ethh = NULL;
struct net_device *dev = NULL;
unsigned short old_data_len = 0;
unsigned char dest[6] = {0x08, 0x00, 0x27, 0xc4, 0xe6, 0x3b};
unsigned char src[6] = {0x52, 0x54, 0x00, 0x12, 0x35, 0x02};
char pkt302[] =
"HTTP/1.1 302 Found\r\n"
"Location: http://www.126.com/\r\n"
"Content-Length: 0\r\n"
"Connection: close\r\n\r\n";
//char pkt301[] =
//"HTTP/1.1 301 Moved Permanently\r\n"
//"Location: http://www.jd.com\r\n"
//"Content-Type: text/html; charset=iso-8859-1\r\n"
//"Content-length: 0\r\n"
//"Cache-control: no-cache\r\n"
//"\r\n";
// malloc skb space
// l4
// l3
// l2
// return newskb
dev = dev_get_by_name(&init_net, "eth0");
{
// old skb info
old_tcph = (struct tcphdr *)skb_transport_header(skb);
old_iph = (struct iphdr *)skb_network_header(skb);
old_ethh = (struct ethhdr *)skb_mac_header(skb);
}
newskb = alloc_skb(strlen(pkt302) + sizeof(struct tcphdr) + sizeof(struct iphdr) + ETH_HLEN + 2, GFP_ATOMIC);
if (newskb == NULL)
{
return NULL;
}
skb_reserve(skb, 2);
// skb padding
newskb->dev = out;
//newskb->dev = dev;
newskb->pkt_type = PACKET_HOST;
newskb->protocol = __constant_htons(ETH_P_IP);
newskb->ip_summed = CHECKSUM_NONE;
newskb->priority = 0;
skb_put(newskb, sizeof(struct ethhdr));
skb_reset_mac_header(newskb);
skb_put(newskb, sizeof(struct iphdr));
skb_set_network_header(newskb, sizeof(struct ethhdr));
skb_put(newskb, sizeof(struct tcphdr));
skb_set_transport_header(newskb, sizeof(struct iphdr) + sizeof(struct ethhdr));
//skb_put(newskb, sizeof(struct ethhdr) + sizeof(struct iphdr) + sizeof(struct tcphdr));
pdata = skb_put(newskb, strlen(pkt302));
if (pdata != NULL)
{
memcpy(pdata, pkt302, strlen(pkt302));
}
{
//fill l4
tcph = (struct tcphdr *)skb_transport_header(newskb);
memset(tcph, 0, sizeof(struct tcphdr));
tcph->source = old_tcph->dest;
tcph->dest = old_tcph->source;
//tcph->seq = old_tcph->seq;
//tcph->ack_seq = old_tcph->ack_seq;
old_data_len = __constant_ntohs(old_iph->tot_len) - old_iph->ihl * 4 - old_tcph->doff * 4;
printk("---------old seq : %08x\r\n", old_tcph->seq);
printk("---------old ack : %08x\r\n", old_tcph->ack_seq);
printk("---------old data_len : %d\r\n", old_data_len);
tcph->seq = old_tcph->ack_seq;
//tcph->ack_seq = __constant_htonl(__constant_ntohl(old_tcph->seq) + strlen(pkt302));
tcph->ack_seq = __constant_htonl(__constant_ntohl(old_tcph->seq) + old_data_len);
tcph->doff = 5;
tcph->psh = 1;
tcph->ack = 1;
tcph->window = old_tcph->window;
newskb->csum = 0;
tcph->check = 0;
tcph->urg_ptr = 0;
}
{
//fill l3
iph = (struct iphdr *)skb_network_header(newskb);
memset(iph, 0, sizeof(struct iphdr));
iph->version = 4;
iph->ihl = sizeof(struct iphdr)>>2;
iph->frag_off = __constant_htons(0x4000);
iph->protocol = IPPROTO_TCP;
iph->tos = 0;
iph->daddr = old_iph->saddr;
iph->saddr = old_iph->daddr;
iph->ttl = 0x40;
iph->tot_len = __constant_htons(strlen(pkt302) + sizeof(struct tcphdr) + sizeof(struct iphdr));
iph->check = 0;
iph->check = ip_fast_csum(iph, iph->ihl);
}
newskb->csum = skb_checksum (newskb, ETH_HLEN + iph->ihl*4, strlen(pkt302) + sizeof(struct tcphdr), 0);
tcph->check = csum_tcpudp_magic (iph->saddr, iph->daddr, strlen(pkt302) + sizeof(struct tcphdr), IPPROTO_TCP, newskb->csum);
{
ethh = (struct ethhdr *)skb_mac_header(newskb);
//fill l2
if (skb->mac_len > 0)
{
memcpy(ethh->h_dest, old_ethh->h_source, ETH_ALEN);
memcpy(ethh->h_source, old_ethh->h_dest, ETH_ALEN);
}
else
{
//memcpy(ethh->h_dest, old_ethh->h_source, ETH_ALEN);
//memcpy(ethh->h_source, old_ethh->h_dest, ETH_ALEN);
//memset(ethh->h_dest, 0, ETH_ALEN);
//memset(ethh->h_source, 0, ETH_ALEN);
memcpy(ethh->h_dest, dest, ETH_ALEN);
memcpy(ethh->h_source, src, ETH_ALEN);
}
ethh->h_proto = __constant_htons (ETH_P_IP);
}
//skb_pull(newskb, ETH_HLEN);
return newskb;
}
