Does TCPdump strip any headers when receiving packets?

Question

So i am attempting to send an already constructed packet over a RAW socket interface (these are packets that have been previously captured and i want to resend them without changing the packet integrity) and am using TCPdump to check that the packets are going over correctly (surprise they are not).

The packets are physically being sent but are always 24 bytes short of what my "sent" returns.

In wireshark my eth headers seem to be erased as my source and dest MAC addresses are "00:00:00:00:00

sock setup is as follows

sock = socket(AF_PACKET,SOCK_RAW,IPPROTO_RAW);
if(sock==-1)
{
    qDebug() << "sock error";
}

int reuse = 1;

if(setsockopt(sock, IPPROTO_RAW, IP_HDRINCL, (char *)&reuse, sizeof(reuse)) < 0)
{
    qDebug() << "error setting reuse"
}
else
{
    "setting reuse"
}

struct sockaddr_ll sll;
struct ifreq ifr;

bzero(&sll, sizeof(sll));
bzero(&ifr, sizeof(ifr));

sll.sll_family = AF_PACKET;
sll.sll_ifindex = ifr.ifr_ifindex;
sll.sll_protocol = htons(IPPROTO_RAW);
sll.sll_halen = ETH_ALEN;

strncpy((char*)ifr.ifr_ifrn.ifrn_name,interface.toUtf8.constData(),IFNAMSIZ);
if(ioctl(sock,SIOCGIFINDEX,&ifr) == -1)
{
   qDebug() << "error getting interface name";
}
strncpy((char*)ifr.ifr_ifrn.ifrn_name,interface.toUtf8.constData(),IFNAMSIZ);
if(ioctl(sock,SIOCGIFHWADDR,&ifr) == -1)
{
   qDebug() << "error getting interface name";
}

if(bind(sock,(struct sockaddr *)&sll,sizeof(sll))==-1)
{
   qDebug() << "error binding sock";
}

after this im using

int size = write(sock,(const void*)&packet,hdr.caplen);

i've tried sendto in the past but it would always reconfigure things so this was my next solution which also isnt working as i would like.

I'm not the most savy with TCP/IP stuff so any help would be greatly appreciated!

Answer 1

okay so after just trying a bunch of different stuff i landed on what seems to be my solution.

i created a second pointer that will point to the top of the packet and send that instead.

(char *)sendingPacket;
struct ethhdr *ethh = (struct ethhdr*)packet;
sendingPacket = (char*) ethh;

i don't really understand why this works but sending the other packet doesn't so if anyone has insight please share!