/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-â
âvi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :viâ
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â Copyright 2020 Justine Alexandra Roberts Tunney                              â
â                                                                              â
â Permission to use, copy, modify, and/or distribute this software for         â
â any purpose with or without fee is hereby granted, provided that the         â
â above copyright notice and this permission notice appear in all copies.      â
â                                                                              â
â THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                â
â WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                â
â WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             â
â AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         â
â DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        â
â PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               â
â TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             â
â PERFORMANCE OF THIS SOFTWARE.                                                â
ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ*/
#include "libc/assert.h"
#include "libc/calls/calls.h"
#include "libc/errno.h"
#include "libc/intrin/cmpxchg.h"
#include "libc/intrin/weaken.h"
#include "libc/mem/mem.h"
#include "libc/nt/errors.h"
#include "libc/nt/iphlpapi.h"
#include "libc/nt/runtime.h"
#include "libc/nt/struct/ipadapteraddresses.h"
#include "libc/nt/winsock.h"
#include "libc/runtime/runtime.h"
#include "libc/sock/internal.h"
#include "libc/sock/sock.h"
#include "libc/sock/struct/ifconf.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/af.h"
#include "libc/sysv/consts/iff.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/errfuns.h"

/* Maximum number of unicast addresses handled for each interface */
#define MAX_UNICAST_ADDR 32
#define MAX_NAME_CLASH   ((int)('z' - 'a')) /* Allow a..z */

struct HostAdapterInfoNode {
  struct HostAdapterInfoNode *next;
  char name[IFNAMSIZ]; /* Obtained from FriendlyName */
  struct sockaddr unicast;
  struct sockaddr netmask;
  struct sockaddr broadcast;
  short flags;
} * __hostInfo;

/* Frees all the nodes of the _hostInfo */
static void freeHostInfo(void) {
  struct HostAdapterInfoNode *next, *node = __hostInfo;
  if (_weaken(free)) {
    while (node) {
      next = node->next;
      _weaken(free)(node);
      node = next;
    }
  }
  __hostInfo = NULL;
}

/* Given a short adapter name, look into __hostInfo to see if there is
 * an adapter with the same name. Returns the pointer to the HostAdapterInfoNode
 * if found, or NULL if not found
 */
static struct HostAdapterInfoNode *findAdapterByName(const char *name) {
  struct HostAdapterInfoNode *node = __hostInfo;
  while (node) {
    if (!strncmp(name, node->name, IFNAMSIZ)) {
      return node;
    }
    node = node->next;
  }
  return NULL;
}

/* Creates a new HostAdapterInfoNode object, initializes it from
 * the given adapter, unicast address and address prefixes
 * and insert it in the __hostInfo.
 * Increments the pointers to the unicast addresses and
 * the address prefixes
 * Returns NULL if an error occurred or the newly created
 * HostAdapterInfoNode object (last in the list)
 */
struct HostAdapterInfoNode *appendHostInfo(
    struct HostAdapterInfoNode *parentInfoNode,
    const char *baseName, /* Max length = IFNAMSIZ-1 */
    const struct NtIpAdapterAddresses
        *aa, /* Top level adapter object being processed */
    struct NtIpAdapterUnicastAddress *
        *ptrUA, /* Ptr to ptr to unicast address list node */
    struct NtIpAdapterPrefix *
        *ptrAP,  /* Ptr to ptr to Adapter prefix list node */
    int count) { /* count is used to create a unique name in case of alias */

  struct HostAdapterInfoNode *temp;
  struct HostAdapterInfoNode *node;
  uint32_t ip, netmask, broadcast;
  struct sockaddr_in *a;
  int attemptNum;

  if (!_weaken(calloc) || !(node = _weaken(calloc)(1, sizeof(*node)))) {
    errno = ENOMEM;
    return NULL;
  }

  memcpy(node->name, baseName, IFNAMSIZ);

  /* Are there more than a single unicast address ? */
  if (count > 0 || ((*ptrUA)->Next != NULL)) {
    /* Yes, compose it using <baseName>:<count> */
    size_t nameLen = strlen(node->name);
    if (nameLen + 2 > IFNAMSIZ - 2) {
      /* Appending the ":x" will exceed the size, need to chop the end */
      nameLen -= 2;
    }
    node->name[nameLen - 2] = ':';
    node->name[nameLen - 1] = '0' + count;
    node->name[nameLen] = '\0';
  }

  /* Is there a name clash with other interfaces? */
  for (attemptNum = 0; attemptNum < MAX_NAME_CLASH; ++attemptNum) {
    temp = findAdapterByName(node->name);
    if (!temp) {
      break;
    } else {
      /* Yes, this name has been already used, append an extra
       * character to resolve conflict. Note since the max length
       * of the string now is IFNAMSIZ-2, we have just enough space for this.
       * E.g. 'Ethernet_1' -> 'Ethernet_1a'
       */
      size_t pos = strlen(node->name);
      node->name[pos] = 'a' + attemptNum;
      node->name[pos + 1] = '\0';
      /* Try again */
    }
  }

  if (attemptNum == MAX_NAME_CLASH) {
    /* Cannot resolve the conflict */
    if (_weaken(free)) {
      _weaken(free)(node);
    }
    errno = EEXIST;
    return NULL;
  }

  /* Finally we got a unique short and friendly name */
  node->unicast = *((*ptrUA)->Address.lpSockaddr);
  if (*ptrUA == aa->FirstUnicastAddress) {
    short flags;
    /* This is the first unicast address of this interface
     * calculate the flags for this adapter. Flags to consider:
     * IFF_UP
     * IFF_BROADCAST        ** TODO: We need to validate
     * IFF_LOOPBACK
     * IFF_POINTOPOINT
     * IFF_MULTICAST
     * IFF_RUNNING          ** Same as IFF_UP for now
     * IFF_PROMISC          ** NOT SUPPORTED, unknown how to retrieve it
     */
    flags = 0;
    if (aa->OperStatus == kNtIfOperStatusUp) flags |= IFF_UP | IFF_RUNNING;
    if (aa->IfType == kNtIfTypePpp) flags |= IFF_POINTOPOINT;
    if (!(aa->Flags & kNtIpAdapterNoMulticast)) flags |= IFF_MULTICAST;
    if (aa->IfType == kNtIfTypeSoftwareLoopback) flags |= IFF_LOOPBACK;
    if (aa->FirstPrefix) flags |= IFF_BROADCAST;
    node->flags = flags;
  } else {
    /* Copy from previous node */
    node->flags = parentInfoNode->flags;
  }

  ip = ntohl(
      ((struct sockaddr_in *)(*ptrUA)->Address.lpSockaddr)->sin_addr.s_addr);
  netmask = (uint32_t)-1 << (32 - (*ptrUA)->OnLinkPrefixLength);
  broadcast = (ip & netmask) | (~netmask & -1);

  a = (struct sockaddr_in *)&node->netmask;
  a->sin_family = AF_INET;
  a->sin_addr.s_addr = htonl(netmask);

  a = (struct sockaddr_in *)&node->broadcast;
  a->sin_family = AF_INET;
  a->sin_addr.s_addr = htonl(broadcast);

  /* Process the prefix and extract the netmask and broadcast */
  /* According to the doc:
   *
   *     On Windows Vista and later, the linked IP_ADAPTER_PREFIX
   *     structures pointed to by the FirstPrefix member include three
   *     IP adapter prefixes for each IP address assigned to the
   *     adapter. These include the host IP address prefix, the subnet
   *     IP address prefix, and the subnet broadcast IP address prefix.
   *     In addition, for each adapter there is a multicast address
   *     prefix and a broadcast address prefix.
   *                   -Source: MSDN on IP_ADAPTER_ADDRESSES_LH
   *
   * For example, interface "Ethernet", with 2 unicast addresses:
   *
   *  - 192.168.1.84
   *  - 192.168.5.99
   *
   * The Prefix list has 8 elements:
   *
   *  #1: 192.168.1.0/24      <- Network, use the PrefixLength for netmask
   *  #2: 192.168.1.84/32     <- Host IP
   *  #3: 192.168.1.255/32    <- Subnet broadcast
   *
   *  #4: 192.168.5.0/24      <- Network
   *  #5: 192.168.5.99/32     <- Host IP
   *  #6: 192.168.5.255/32    <- Subnet broadcast
   *
   *  #7: 224.0.0.0/4         <- Multicast
   *  #8: 255.255.255.255/32  <- Broadcast
   */

  if (ptrAP && *ptrAP) {
    *ptrAP = (*ptrAP)->Next; /* skip net ip */
    if (*ptrAP) {
      *ptrAP = (*ptrAP)->Next; /* skip host ip */
      if (*ptrAP) {
        node->broadcast = *((*ptrAP)->Address.lpSockaddr);
      }
    }
  }

  *ptrUA = (*ptrUA)->Next;

  /* Append this node to the last node (if any) */
  if (parentInfoNode) {
    parentInfoNode->next = node;
  }

  /* Success */
  return node;
}

/* Returns -1 in case of failure */
static int createHostInfo(struct NtIpAdapterAddresses *firstAdapter) {
  static bool once;
  struct NtIpAdapterAddresses *aa;
  struct NtIpAdapterUnicastAddress *ua;
  struct NtIpAdapterPrefix *ap;
  struct HostAdapterInfoNode *node = NULL;
  char baseName[IFNAMSIZ];
  char name[IFNAMSIZ];
  int count, i;

  /* __hostInfo must be empty */
  _unassert(__hostInfo == NULL);

  for (aa = firstAdapter; aa; aa = aa->Next) {
    /* Skip all the interfaces with no address and the ones that are not AF_INET
     */
    if (!aa->FirstUnicastAddress ||
        aa->FirstUnicastAddress->Address.lpSockaddr->sa_family != AF_INET) {
      continue;
    }

    /* Use max IFNAMSIZ-1 chars, leave the last char for eventual conflicts */
    tprecode16to8(baseName, IFNAMSIZ - 1, aa->FriendlyName);
    baseName[IFNAMSIZ - 2] = '\0';
    /* Replace any space with a '_' */
    for (i = 0; i < IFNAMSIZ - 2; ++i) {
      if (baseName[i] == ' ') baseName[i] = '_';
      if (!baseName[i]) break;
    }
    for (count = 0, ua = aa->FirstUnicastAddress, ap = aa->FirstPrefix;
         (ua != NULL) && (count < MAX_UNICAST_ADDR); ++count) {
      node = appendHostInfo(node, baseName, aa, &ua, &ap, count);
      if (!node) goto err;
      if (!__hostInfo) {
        __hostInfo = node;
        if (_cmpxchg(&once, false, true)) {
          atexit(freeHostInfo);
        }
      }
    }

    /* Note: do we need to process the remaining adapter prefix?
     *      ap       - points to broadcast addr
     *      ap->Next - points to interface multicast addr
     * Ignoring them for now
     */
  }
  return 0;

err:
  freeHostInfo();
  return -1;
}

static int readAdapterAddresses(void) {
  uint32_t size, rc;
  struct NtIpAdapterAddresses *aa = NULL;

  /* Calculate the required data size
   * Note: alternatively you can use AF_UNSPEC to also return IPv6 interfaces
   */
  rc = GetAdaptersAddresses(AF_INET,
                            kNtGaaFlagSkipAnycast | kNtGaaFlagSkipMulticast |
                                kNtGaaFlagSkipDnsServer |
                                kNtGaaFlagIncludePrefix,
                            NULL, /* Reserved */
                            NULL, /* Ptr */
                            &size);
  if (rc != kNtErrorBufferOverflow) {
    ebadf();
    goto err;
  }

  if (!_weaken(malloc) ||
      !(aa = (struct NtIpAdapterAddresses *)_weaken(malloc)(size))) {
    enomem();
    goto err;
  }

  /* Re-run GetAdaptersAddresses this time with a valid buffer */
  rc = GetAdaptersAddresses(AF_INET,
                            kNtGaaFlagSkipAnycast | kNtGaaFlagSkipMulticast |
                                kNtGaaFlagSkipDnsServer |
                                kNtGaaFlagIncludePrefix,
                            // kNtGaaFlagIncludePrefix,
                            NULL, aa, &size);
  if (rc != kNtErrorSuccess) {
    errno = GetLastError();
    goto err;
  }
  if (createHostInfo(aa) == -1) {
    goto err;
  }

  if (_weaken(free)) {
    _weaken(free)(aa);
  }
  return 0;

err:
  if (_weaken(free)) {
    _weaken(free)(aa);
  }
  freeHostInfo();
  return -1;
}

textwindows int ioctl_siocgifconf_nt(int fd, struct ifconf *ifc) {
  struct NtIpAdapterAddresses *aa;
  struct HostAdapterInfoNode *node;
  struct ifreq *ptr;

  if (__hostInfo) {
    freeHostInfo();
  }

  if (readAdapterAddresses() == -1) {
    return -1;
  }

  for (ptr = ifc->ifc_req, node = __hostInfo;
       (((char *)(ptr + 1) - ifc->ifc_buf) < ifc->ifc_len) && node;
       ptr++, node = node->next) {
    memcpy(ptr->ifr_name, node->name, IFNAMSIZ);
    memcpy(&ptr->ifr_addr, &node->unicast, sizeof(struct sockaddr));
  }
  ifc->ifc_len = (char *)ptr - ifc->ifc_buf;

  return 0;
}

/**
 * Returns unicast addresses.
 */
int ioctl_siocgifaddr_nt(int fd, struct ifreq *ifr) {
  struct HostAdapterInfoNode *node;
  node = findAdapterByName(ifr->ifr_name);
  if (!node) return ebadf();
  memcpy(&ifr->ifr_addr, &node->unicast, sizeof(struct sockaddr));
  return 0;
}

/* Performs the SIOCGIFFLAGS operation */
int ioctl_siocgifflags_nt(int fd, struct ifreq *ifr) {
  struct HostAdapterInfoNode *node;
  node = findAdapterByName(ifr->ifr_name);
  if (!node) return ebadf();
  ifr->ifr_flags = node->flags;
  return 0;
}

/* Performs the SIOCGIFNETMASK operation */
int ioctl_siocgifnetmask_nt(int fd, struct ifreq *ifr) {
  struct HostAdapterInfoNode *node;
  node = findAdapterByName(ifr->ifr_name);
  if (!node) return ebadf();
  memcpy(&ifr->ifr_netmask, &node->netmask, sizeof(struct sockaddr));
  return 0;
}

/**
 * Returns broadcast address.
 */
int ioctl_siocgifbrdaddr_nt(int fd, struct ifreq *ifr) {
  struct HostAdapterInfoNode *node;
  node = findAdapterByName(ifr->ifr_name);
  if (!node) return ebadf();
  memcpy(&ifr->ifr_broadaddr, &node->broadcast, sizeof(struct sockaddr));
  return 0;
}
