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valid ip-id

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PoliEcho
2026-09-18 20:39:04 +02:00
parent 5effc8541c
commit 7c4d977a62
1 changed files with 11 additions and 0 deletions
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src/main.c
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@@ -16,6 +16,7 @@
#define IPV4_TTL_OFFSET 8 #define IPV4_TTL_OFFSET 8
#define IPV4_ID_OFFSET 4
#define IPV4_PROTOCOL_OFFSET 9 #define IPV4_PROTOCOL_OFFSET 9
#define IPV4_CHECKSUM_OFFSET 10 #define IPV4_CHECKSUM_OFFSET 10
#define IPV4_SRC_ADDR_OFFSET 12 #define IPV4_SRC_ADDR_OFFSET 12
@@ -34,6 +35,7 @@
#define TCP_SRC_PORT_OFFSET 0 #define TCP_SRC_PORT_OFFSET 0
#define TCP_SEQ_OFFSET 4 #define TCP_SEQ_OFFSET 4
#define TCP_ACK_NUM_OFFSET 8
#define TCP_DATA_OFFSET_OFFSET 12 #define TCP_DATA_OFFSET_OFFSET 12
#define TCP_DATA_OFFSET_SHIFT 4 #define TCP_DATA_OFFSET_SHIFT 4
@@ -230,6 +232,11 @@ int xdp_drop_prog(struct xdp_md *ctx) {
*tcp_flags_ptr = tcp_flags | ACK_MASK; *tcp_flags_ptr = tcp_flags | ACK_MASK;
// set ISN and ack number
*(__u32 *)(tcp_packet_data + TCP_ACK_NUM_OFFSET) = bpf_htonl(
bpf_ntohl(*(__u32 *)(tcp_packet_data + TCP_SEQ_OFFSET))+1);
*(__u32 *)(tcp_packet_data + TCP_SEQ_OFFSET) = bpf_get_prandom_u32();
*(__u16 *)(tcp_packet_data + TCP_CHECKSUM_OFFSET) = 0; // must be zero for calculation *(__u16 *)(tcp_packet_data + TCP_CHECKSUM_OFFSET) = 0; // must be zero for calculation
const __u8 tcp_data_offset = const __u8 tcp_data_offset =
@@ -278,6 +285,10 @@ int xdp_drop_prog(struct xdp_md *ctx) {
*ipv4_checksum_ptr = bpf_htons((__u16)new_checksum); *ipv4_checksum_ptr = bpf_htons((__u16)new_checksum);
} }
// set ID
*(__u16*)(ip_packet_data+IPV4_ID_OFFSET) = bpf_get_prandom_u32();
struct tcp_v4_pseudo_header pseudo_header = { struct tcp_v4_pseudo_header pseudo_header = {
*src_ip_ptr, *dst_ip_ptr, 0, TCP_PROTO_ID, *src_ip_ptr, *dst_ip_ptr, 0, TCP_PROTO_ID,
bpf_htons(data_end - tcp_packet_data)}; bpf_htons(data_end - tcp_packet_data)};