Create and Send Packet from Scratch
Hi all, In my schoool project (kernel 2.2.X), I would like to pass some data attached immediately above IP. (i.e. w/o UDP and TCP) I have assigned an arbitrary protocol # in the IP header field so that the received data is passed on to my protocol stack. There is no problem on reception but I got stuck at all the transmission and forwarding operations: 1, How can I transmit data by using a sk_buff that is created from scratch? 2, How can I forward data from the sk_buff of a received packet. I have run some trial codes (attached below) but the kernel crashes. Is my description clear? I surely have missed out something but I have no clue. Could anyone point out what is missing from my code? Thanks in advance. :) == Transmit Data from Scratch (version 1) == /* this is how I try the thing out */ struct sk_buff *skb=alloc_skb(sizeof(struct iphdr)+15,GFP_ATOMIC) skb_put(skb,data_len); memcpy(skb->data,data_ptr,data_len); ip_route_output(, [some dst addr in __u32] , 0, RT_TOS(0), 0); iph = (struct iphdr*) skb->nh.iph; iph->version = 4; iph->ihl = sizeof(struct iphdr) >> 2; iph->tos = 0; iph->tot_len = htons(skb->len); iph->id = htons(ip_id_count++); iph->frag_off = 0; iph->ttl = 64; iph->protocol = [some self-defined #]; iph->saddr = rt->rt_src; iph->daddr = rt->rt_dst; ip_send_check(iph); skb->dst = >u.dst; skb->dst->output(skb); == Transmit Data from Scratch (version 2) == /* code that I find somewhere else */ /* my comment */ [original comment] skb->dev = [put device here]; /* = ip_dev_find(daddr); ? */ skb->nh.iph->saddr = [alter the saddress to this m/c] /* Is there a "raddr" in "include/linux/ip.h"? */ skb->nh.iph->raddr = [alter the router address] if(!skb->dst) [allocate dst_entry stucture] /* how can I do this? :p */ rt = (struct rtable *) skb->dst; ip_route_output(, skb->nh.iph->raddr, skb->nh.iph->saddr, 1, 0 ) hdr = (struct ethhdr *)skb_push( skb, ETH_HLEN); memcpy(hdr->h_source, skb->dev->dev_addr, skb->dev->addr_len); hdr->h_proto = __constant_htons(ETH_P_IP); arp_find(skb->dev->h_dest, skb); dev_queue_xmit(skb); === Forward Data of Received Packet === /* just alter the destination IP address */ /* or may add some data as well */ /* and then send it out */ /* outgoing device may be different from incoming device */ /* skb is the received skb */ struct rtable *rt; struct iphdr *iph; struct sk_buff *skb2; skb2 = skb_copy(skb, GFP_KERNEL); iph = (struct iphdr*) skb2->nh.iph; ip_route_output(, [some dst addr in __u32] , 0, RT_TOS(0), 0); iph->daddr = [some dst addr in __u32]; /* // if I add 4 bytes of data as well iph->tot_len = htons(ntohs(iph->tot_len) + 4); skb->tail += 4; skb->len += 4; */ ip_send_check(iph); skb2->dst = >u.dst; skb2->dst->output(skb2); Get your own FREE, personal Netscape WebMail account today at http://home.netscape.com/webmail - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/
Create and Send Packet from Scratch
Hi all, In my schoool project (kernel 2.2.X), I would like to pass some data attached immediately above IP. (i.e. w/o UDP and TCP) I have assigned an arbitrary protocol # in the IP header field so that the received data is passed on to my protocol stack. There is no problem on reception but I got stuck at all the transmission and forwarding operations: 1, How can I transmit data by using a sk_buff that is created from scratch? 2, How can I forward data from the sk_buff of a received packet. I have run some trial codes (attached below) but the kernel crashes. Is my description clear? I surely have missed out something but I have no clue. Could anyone point out what is missing from my code? Thanks in advance. :) == Transmit Data from Scratch (version 1) == /* this is how I try the thing out */ struct sk_buff *skb=alloc_skb(sizeof(struct iphdr)+15,GFP_ATOMIC) skb_put(skb,data_len); memcpy(skb-data,data_ptr,data_len); ip_route_output(rt, [some dst addr in __u32] , 0, RT_TOS(0), 0); iph = (struct iphdr*) skb-nh.iph; iph-version = 4; iph-ihl = sizeof(struct iphdr) 2; iph-tos = 0; iph-tot_len = htons(skb-len); iph-id = htons(ip_id_count++); iph-frag_off = 0; iph-ttl = 64; iph-protocol = [some self-defined #]; iph-saddr = rt-rt_src; iph-daddr = rt-rt_dst; ip_send_check(iph); skb-dst = rt-u.dst; skb-dst-output(skb); == Transmit Data from Scratch (version 2) == /* code that I find somewhere else */ /* my comment */ [original comment] skb-dev = [put device here]; /* = ip_dev_find(daddr); ? */ skb-nh.iph-saddr = [alter the saddress to this m/c] /* Is there a "raddr" in "include/linux/ip.h"? */ skb-nh.iph-raddr = [alter the router address] if(!skb-dst) [allocate dst_entry stucture] /* how can I do this? :p */ rt = (struct rtable *) skb-dst; ip_route_output(rt, skb-nh.iph-raddr, skb-nh.iph-saddr, 1, 0 ) hdr = (struct ethhdr *)skb_push( skb, ETH_HLEN); memcpy(hdr-h_source, skb-dev-dev_addr, skb-dev-addr_len); hdr-h_proto = __constant_htons(ETH_P_IP); arp_find(skb-dev-h_dest, skb); dev_queue_xmit(skb); === Forward Data of Received Packet === /* just alter the destination IP address */ /* or may add some data as well */ /* and then send it out */ /* outgoing device may be different from incoming device */ /* skb is the received skb */ struct rtable *rt; struct iphdr *iph; struct sk_buff *skb2; skb2 = skb_copy(skb, GFP_KERNEL); iph = (struct iphdr*) skb2-nh.iph; ip_route_output(rt, [some dst addr in __u32] , 0, RT_TOS(0), 0); iph-daddr = [some dst addr in __u32]; /* // if I add 4 bytes of data as well iph-tot_len = htons(ntohs(iph-tot_len) + 4); skb-tail += 4; skb-len += 4; */ ip_send_check(iph); skb2-dst = rt-u.dst; skb2-dst-output(skb2); Get your own FREE, personal Netscape WebMail account today at http://home.netscape.com/webmail - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/
