Question

There are two problems here:

1. What if content is encoded:gzip…
2. Do I also need to change the header part to make the HTTP packet valid(checksums if any?)

UPDATE

Can someone with actual experience elaborate the steps involved?

I’m using winpcap and bpf tcp and src port 80 to filter the traffic,so my job lies in this callback function:

void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data)

Answer 1

WinPcap doesn’t allow you to change a packet that was already sent.

If the packet was sent, WinPcap won’t prevent it from reaching its destination.

If you want to send another response – in addition to the response that was sent – I’m not sure what you’re trying to achieve.