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Arbitrary payload expansion is now working. IP checksum recomputation needs a revision, it is always 0...

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h3xduck
2021-11-25 20:30:15 -05:00
parent 253c302695
commit ca23880fd4
9 changed files with 940 additions and 609 deletions
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13
src/include/xdp/xdp_helper.h
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@@ -1,6 +1,8 @@
#ifndef __XDP_HELPER_H__
#define __XDP_HELPER_H__
#include <linux/types.h>
#include <bpf/bpf_helpers.h>
#include "packet/protocol/ip_helper.h"
@@ -9,7 +11,7 @@
static struct expand_return{
int code;
struct xdp_md ret_md;
struct xdp_md *ret_md;
void *data;
void *data_end;
struct ethhdr *eth;
@@ -81,10 +83,13 @@ static __always_inline struct expand_return expand_tcp_packet_payload(struct xdp
//We modify the fields we care about of the headers
bpf_printk("before: %i\n", ret.ip->tot_len);
bpf_printk("before: %i, checksum %u\n", ret.ip->tot_len, ret.ip->check);
ret.ip->tot_len = htons(ntohs(ret.ip->tot_len) + more_bytes);
bpf_printk("after: %i\n", ret.ip->tot_len);
ret.ret_md = *ctx;
uint32_t csum = 0;
ipv4_csum(ret.ip, sizeof(struct iphdr), &csum);
ret.ip->check = csum;
bpf_printk("after: %i, checksum %u\n", ret.ip->tot_len, ret.ip->check);
ret.ret_md = ctx;
ret.code = 0;
ret.data = (void *)(long)ctx->data;
ret.data_end = (void *)(long)ctx->data_end;