Add packet_build.cpp support imitate_tcp_packet() / imitate_udp_packet()

src/packet/checksum.cpp

@@ -0,0 +1,111 @@
+#include "checksum.h"
+
+#include <arpa/inet.h>
+
+uint16_t checksum(const char *data, uint16_t len)
+{
+    uint32_t sum = 0;
+    const uint16_t *ip1 = (const uint16_t *)data;
+
+    while (len > 1)
+    {
+        sum += *ip1++;
+        if (sum & 0x80000000)
+        {
+            sum = (sum & 0xFFFF) + (sum >> 16);
+        }
+        len -= 2;
+    }
+
+    while (sum >> 16)
+    {
+        sum = (sum & 0xFFFF) + (sum >> 16);
+    }
+
+    return (~sum);
+}
+
+uint16_t checksum_v4(const void *l4_hdr_ptr, uint16_t l4_total_len, uint8_t l4_proto, struct in_addr *src_addr, struct in_addr *dst_addr)
+{
+    uint16_t *ip_src = (uint16_t *)src_addr;
+    uint16_t *ip_dst = (uint16_t *)dst_addr;
+    const uint16_t *buffer = (u_int16_t *)l4_hdr_ptr;
+
+    uint32_t sum = 0;
+    size_t len = l4_total_len;
+
+    while (len > 1)
+    {
+        sum += *buffer++;
+        if (sum & 0x80000000)
+        {
+            sum = (sum & 0xFFFF) + (sum >> 16);
+        }
+        len -= 2;
+    }
+
+    if (len & 1)
+    {
+        sum += *((uint8_t *)buffer);
+    }
+
+    sum += *(ip_src++);
+    sum += *ip_src;
+    sum += *(ip_dst++);
+    sum += *ip_dst;
+    sum += htons(l4_proto);
+    sum += htons(l4_total_len);
+
+    while (sum >> 16)
+    {
+        sum = (sum & 0xFFFF) + (sum >> 16);
+    }
+
+    return ((uint16_t)(~sum));
+}
+
+uint16_t checksum_v6(const void *l4_hdr_ptr, uint16_t l4_total_len, uint8_t l4_proto, struct in6_addr *src_addr, struct in6_addr *dst_addr)
+{
+    uint16_t *ip_src = (uint16_t *)src_addr;
+    uint16_t *ip_dst = (uint16_t *)dst_addr;
+    const uint16_t *buffer = (u_int16_t *)l4_hdr_ptr;
+
+    uint32_t sum = 0;
+    size_t len = l4_total_len;
+
+    while (len > 1)
+    {
+        sum += *buffer++;
+        if (sum & 0x80000000)
+        {
+            sum = (sum & 0xFFFF) + (sum >> 16);
+        }
+        len -= 2;
+    }
+
+    if (len & 1)
+    {
+        sum += *((uint8_t *)buffer);
+    }
+
+    for (int i = 0; i < 8; i++)
+    {
+        sum += *ip_src;
+        ip_src++;
+    }
+
+    for (int i = 0; i < 8; i++)
+    {
+        sum += *ip_dst;
+        ip_dst++;
+    }
+    sum += htons(l4_proto);
+    sum += htons(l4_total_len);
+
+    while (sum >> 16)
+    {
+        sum = (sum & 0xFFFF) + (sum >> 16);
+    }
+
+    return ((uint16_t)(~sum));
+}