C What's Wrong?

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>

#define ALLOWED_IP "127.3.3.1"

int main() {
    char ip_addr[128];
    struct in_addr to_ping_host, trusted_host;

    // get address
    if (!fgets(ip_addr, sizeof(ip_addr), stdin))
        return 1;
    ip_addr[strcspn(ip_addr, "\n")] = 0;

    // verify address
    if (!inet_aton(ip_addr, &to_ping_host))
        return 1;
    char *ip_addr_resolved = inet_ntoa(to_ping_host);

    // prevent SSRF
    if ((ntohl(to_ping_host.s_addr) >> 24) == 127)
        return 1;

    // only allowed
    if (!inet_aton(ALLOWED_IP, &trusted_host))
        return 1;
    char *trusted_resolved = inet_ntoa(trusted_host);

    if (strcmp(ip_addr_resolved, trusted_resolved) != 0)
        return 1;

    // ping
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "ping '%s'", ip_addr);
    system(cmd);
    return 0;
}

NTSTATUS
InitServiceCallback(
  _In_ WDFREQUEST Request
)
{
  NTSTATUS status;
  PWCHAR regPath = NULL;
  size_t bufferLength = 0;

  // fetch the product registry path from the request
  status = WdfRequestRetrieveInputBuffer(
    Request, 4, &regPath, &bufferLength);
  if (!NT_SUCCESS(status))
  {
    TraceEvents(
      TRACE_LEVEL_ERROR,
      TRACE_QUEUE,
      "%!FUNC! Failed to retrieve input buffer."
      " Status: %d", (int)status
    );
    return status;
  }
  /* check that the buffer size is a null-terminated
     Unicode (UTF-16) string of a sensible size */
  if (bufferLength < 4 ||
    bufferLength > 512 ||
    (bufferLength % 2) != 0 ||
    regPath[(bufferLength / 2) - 1] != L'\0')
  {
    TraceEvents(
      TRACE_LEVEL_ERROR,
      TRACE_QUEUE,
      "%!FUNC! Buffer length %d was incorrect.",
      (int)bufferLength
    );
    return STATUS_INVALID_PARAMETER;
  }

  ProductVersionInfo version = { 0 };
  HandlerCallback handlerCallback = NewCallback;
  int readValue = 0;
  // read the major version from the registry
  RTL_QUERY_REGISTRY_TABLE regQueryTable[2];
  RtlZeroMemory(
    regQueryTable,
    sizeof(RTL_QUERY_REGISTRY_TABLE) * 2);
  regQueryTable[0].Name = L"MajorVersion";
  regQueryTable[0].EntryContext = &readValue;
  regQueryTable[0].Flags = RTL_QUERY_REGISTRY_DIRECT;
  regQueryTable[0].QueryRoutine = NULL;
  status = RtlQueryRegistryValues(
    RTL_REGISTRY_ABSOLUTE,
    regPath,
    regQueryTable,
    NULL,
    NULL
  );
  if (!NT_SUCCESS(status))
  {
    TraceEvents(
      TRACE_LEVEL_ERROR,
      TRACE_QUEUE,
      "%!FUNC! Failed to query registry."
      " Status: %d", (int)status
    );
    return status;
  }
  TraceEvents(
    TRACE_LEVEL_INFORMATION,
    TRACE_QUEUE,
    "%!FUNC! Major version is %d",
    (int)readValue
  );
  version.Major = readValue;
  if (version.Major < 3)
  {
    // versions prior to 3.0 need an additional check
    RtlZeroMemory(
      regQueryTable,
      sizeof(RTL_QUERY_REGISTRY_TABLE) * 2);
    regQueryTable[0].Name = L"MinorVersion";
    regQueryTable[0].EntryContext = &readValue;
    regQueryTable[0].Flags =
      RTL_QUERY_REGISTRY_DIRECT;
    regQueryTable[0].QueryRoutine = NULL;
    status = RtlQueryRegistryValues(
      RTL_REGISTRY_ABSOLUTE,
      regPath,
      regQueryTable,
      NULL,
      NULL
    );
    if (!NT_SUCCESS(status))
    {
      TraceEvents(
        TRACE_LEVEL_ERROR,
        TRACE_QUEUE,
        "%!FUNC! Failed to query registry."
        " Status: %d",
        (int)status
      );
      return status;
    }
    TraceEvents(
      TRACE_LEVEL_INFORMATION,
      TRACE_QUEUE,
      "%!FUNC! Minor version is %d",
      (int)readValue
    );
    version.Minor = readValue;
    if (!DoesVersionSupportNewCallback(version))
    {
      handlerCallback = OldCallback;
    }
  }
  SetGlobalHandlerCallback(handlerCallback);
}