How to debug "Malformed Packet (Exception occurred)" when send a udp packet?

[lx]

Thank you. I make a error with "tot_len".

2014-09-16 23:05 GMT+08:00 ankur dwivedi <ankurengg2003 at gmail.com>:

> What is getting shown in tcpdump?
>
> I guess its a checksum problem.
>
> On Sun, Sep 7, 2014 at 2:42 PM, lx <lxlenovostar at gmail.com> wrote:
>
>> hi all:
>>       I want to send a udp packet in kernel module. the codes is:
>> ####################################################
>>                        /*
>> * send UDP packet
>> */
>> char *dest_addr = "192.168.109.176";
>> int eth_len, udph_len, iph_len, len;
>> eth_len = sizeof(struct ethhdr);
>> iph_len = sizeof(struct iphdr);
>> udph_len  = sizeof(struct udphdr);
>> len = eth_len + iph_len + udph_len;
>>
>> struct sk_buff *send_skb = alloc_skb(len, GFP_ATOMIC);
>> if (!send_skb)
>> return NF_DROP;
>>
>> //skb_put(send_skb, len);
>> skb_reserve(send_skb, len);
>>
>> skb_push(send_skb, sizeof(struct udphdr));
>>
>> skb_reset_transport_header(send_skb);
>>  udph = udp_hdr(send_skb);
>> udph->source = dport;
>> udph->dest = dport;
>> udph->len = htons(udph_len);
>> udph->check = 0;
>> udph->check = csum_tcpudp_magic(daddr, in_aton(dest_addr), udph_len,
>> IPPROTO_UDP, csum_partial(udph, udph_len, 0));
>>  //if (udph->check == 0)
>> // udph->check = CSUM_MANGLED_0;
>>
>> skb_push(send_skb, sizeof(struct iphdr));
>> skb_reset_network_header(send_skb);
>> send_iph = ip_hdr(send_skb);
>>
>> // iph->version = 4; iph->ihl = 5;
>> put_unaligned(0x45, (unsigned char *)send_iph);
>> send_iph->tos      = 0;
>> put_unaligned(htons(iph_len), &(send_iph->tot_len));
>> //send_iph->id       = htons(atomic_inc_return(&ip_ident));
>> send_iph->id       = 0;
>> send_iph->frag_off = 0;
>> send_iph->ttl      = 64;
>> send_iph->protocol = IPPROTO_UDP;
>> send_iph->check    = 0;
>> put_unaligned(daddr, &(send_iph->saddr));
>> put_unaligned(in_aton(dest_addr), &(send_iph->daddr));
>> send_iph->check    = ip_fast_csum((unsigned char *)send_iph,
>> send_iph->ihl);
>>
>> eth = (struct ethhdr *) skb_push(send_skb, ETH_HLEN);
>> skb_reset_mac_header(send_skb);
>> send_skb->protocol = eth->h_proto = htons(ETH_P_IP);
>> memcpy(eth->h_source, dev->dev_addr, ETH_ALEN);
>> memcpy(eth->h_dest, "00:0C:29:DC:2D:F5", ETH_ALEN);
>>
>> send_skb->dev = dev;
>> dev_queue_xmit(send_skb);
>> ####################################################
>>
>> I think the udp packe is sent,but the wirshark detect this packet is
>> error.
>> The Error message is:
>> ####################################################
>>
>> ​
>> ####################################################
>>
>> Tell me how to debug it? I'm a new one,
>> Thank you.
>>
>>
>>
>>
>>
>>
>>
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>>
>>
>
>
> --
>
>
> --
>
> ankur dwivedi
> http://about.me/ankur_dwivedi
>
>
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