/* netstat.c - Display Linux networking subsystem.
 *
 * Copyright 2012 Ranjan Kumar <ranjankumar.bth@gmail.com>
 * Copyright 2013 Kyungwan Han <asura321@gmail.com>
 *
 * Not in SUSv4.
 *
USE_NETSTAT(NEWTOY(netstat, "pWrxwutneal", TOYFLAG_BIN))
config NETSTAT
  bool "netstat"
  default n
  help
    usage: netstat [-pWrxwutneal]

    Display networking information.

    -r  Display routing table.
    -a  Display all sockets (Default: Connected).
    -l  Display listening server sockets.
    -t  Display TCP sockets.
    -u  Display UDP sockets.
    -w  Display Raw sockets.
    -x  Display Unix sockets.
    -e  Display other/more information.
    -n  Don't resolve names.
    -W  Wide Display.
    -p  Display PID/Program name for sockets.
*/

#define FOR_netstat
#include "toys.h"

#include <net/route.h>

GLOBALS(
  char current_name[21];
  int some_process_unidentified;
);

typedef union _iaddr {
  unsigned u;
  unsigned char b[4];
} iaddr;

typedef union _iaddr6 {
  struct {
    unsigned a;
    unsigned b;
    unsigned c;
    unsigned d;
  } u;
  unsigned char b[16];
} iaddr6;

#define ADDR_LEN (INET6_ADDRSTRLEN + 1 + 5 + 1)//IPv6 addr len + : + port + '\0'

//For unix states
enum {
	SOCK_ACCEPTCON = (1 << 16),  //performed a listen.
	SOCK_WAIT_DATA = (1 << 17),  //wait data to read.
	SOCK_NO_SPACE = (1 << 18),  //no space to write.
};

#define SOCK_NOT_CONNECTED 1

typedef struct _pidlist {
  struct _pidlist *next;
  long inode;
  char name[21];
} PID_LIST;

PID_LIST *pid_list = NULL;

/*
 * used to convert string into int and
 * validate the input str for invalid int value or out-of-range.
 */
static unsigned long get_strtou(char *str, char **endp, int base)
{
  unsigned long uli;
  char *endptr;

  if (!isalnum(str[0])) {
    errno = ERANGE;
    return UINT_MAX;
  }
  errno = 0;
  uli = strtoul(str, &endptr, base);
  if (uli > UINT_MAX) {
    errno = ERANGE;
    return UINT_MAX;
  }

  if (endp) *endp = endptr;
  if (endptr[0]) {
    if (isalnum(endptr[0]) || errno) { //"123abc" or out-of-range
      errno = ERANGE;
      return UINT_MAX;
    }
    errno = EINVAL;
  }
  return uli;
}

/*
 * used to retrive pid name from pid list.
 */
static const char *get_pid_name(unsigned long inode)
{
  PID_LIST *tmp;

  for (tmp = pid_list; tmp; tmp = tmp->next)
    if (tmp->inode == inode) return tmp->name;

  return "-";
}

/*
 * For TCP/UDP/RAW display data.
 */
static void display_data(unsigned rport, char *label,
                         unsigned rxq, unsigned txq, char *lip, char *rip,
                         unsigned state, unsigned uid, unsigned long inode)
{
  char *ss_state = "UNKNOWN", buf[12];
  char *state_label[] = {"", "ESTABLISHED", "SYN_SENT", "SYN_RECV", "FIN_WAIT1",
                         "FIN_WAIT2", "TIME_WAIT", "CLOSE", "CLOSE_WAIT",
                         "LAST_ACK", "LISTEN", "CLOSING", "UNKNOWN"};
  char user[11];
  struct passwd *pw;

  if (!strcmp(label, "tcp")) {
    int sz = ARRAY_LEN(state_label);
    if (!state || state >= sz) state = sz-1;
    ss_state = state_label[state];
  }
  else if (!strcmp(label, "udp")) {
    if (state == 1) ss_state = state_label[state];
    else if (state == 7) ss_state = "";
  }
  else if (!strcmp(label, "raw")) sprintf(ss_state = buf, "%u", state);

  if (!(toys.optflags & FLAG_n) && (pw = getpwuid(uid))) {
    snprintf(user, sizeof(user), "%s", pw->pw_name);
  } else snprintf(user, sizeof(user), "%d", uid);

  xprintf("%3s   %6d %6d ", label, rxq, txq);
  xprintf((toys.optflags & FLAG_W) ? "%-51.51s %-51.51s " : "%-23.23s %-23.23s "
           , lip, rip);
  xprintf("%-11s", ss_state);
  if ((toys.optflags & FLAG_e)) xprintf(" %-10s %-11ld", user, inode);
  if ((toys.optflags & FLAG_p)) xprintf(" %s", get_pid_name(inode));
  xputc('\n');
}

/*
 * For TCP/UDP/RAW show data.
 */
static void show_data(unsigned rport, char *label, unsigned rxq, unsigned txq,
                      char *lip, char *rip, unsigned state, unsigned uid,
                      unsigned long inode)
{
  if (toys.optflags & FLAG_l) {
    if (!rport && (state & 0xA))
      display_data(rport, label, rxq, txq, lip, rip, state, uid, inode);
  } else if (toys.optflags & FLAG_a)
    display_data(rport, label, rxq, txq, lip, rip, state, uid, inode);
  //rport && (TCP | UDP | RAW)
  else if (rport & (0x10 | 0x20 | 0x40))
    display_data(rport, label, rxq, txq, lip, rip, state, uid, inode);
}

/*
 * used to get service name.
 */
static char *get_servname(int port, char *label)
{
  int lport = htons(port);
  if (!lport) return xmprintf("%s", "*");
  struct servent *ser = getservbyport(lport, label);
  if (ser) return xmprintf("%s", ser->s_name);
  return xmprintf("%u", (unsigned)ntohs(lport));
}

/*
 * used to convert address into text format.
 */
static void addr2str(int af, void *addr, unsigned port, char *buf, char *label)
{
  char ip[ADDR_LEN] = {0,};
  if (!inet_ntop(af, addr, ip, ADDR_LEN)) {
    *buf = '\0';
    return;
  }
  size_t iplen = strlen(ip);
  if (!port) {
    strncat(ip+iplen, ":*", ADDR_LEN-iplen-1);
    memcpy(buf, ip, ADDR_LEN);
    return;
  }

  if (!(toys.optflags & FLAG_n)) {
    struct addrinfo hints, *result, *rp;

    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_family = af;

    if (!getaddrinfo(ip, NULL, &hints, &result)) {
      char hbuf[NI_MAXHOST] = {0,}, sbuf[NI_MAXSERV] = {0,};
      socklen_t sock_len;
      char *sname = NULL;
      int plen = 0;

      if (af == AF_INET) sock_len = sizeof(struct sockaddr_in);
      else sock_len = sizeof(struct sockaddr_in6);

      for (rp = result; rp; rp = rp->ai_next)
        if (!getnameinfo(rp->ai_addr, sock_len, hbuf, sizeof(hbuf), sbuf,
            sizeof(sbuf), NI_NUMERICSERV))
          break;

      freeaddrinfo(result);
      sname = get_servname(port, label);
      plen = strlen(sname);
      if (*hbuf) {
        memset(ip, 0, ADDR_LEN);
        memcpy(ip, hbuf, (ADDR_LEN - plen - 2));
        iplen = strlen(ip);
      }
      snprintf(ip + iplen, ADDR_LEN-iplen, ":%s", sname);
      free(sname);
    }
  }
  else snprintf(ip+iplen, ADDR_LEN-iplen, ":%d", port);
  memcpy(buf, ip, ADDR_LEN);
}

/*
 * display ipv4 info for TCP/UDP/RAW.
 */
static void show_ipv4(char *fname, char *label)
{
  FILE *fp = fopen(fname, "r");
  if (!fp) {
     perror_msg("'%s'", fname);
     return;
  }

  if(!fgets(toybuf, sizeof(toybuf), fp)) return; //skip header.

  while (fgets(toybuf, sizeof(toybuf), fp)) {
    char lip[ADDR_LEN] = {0,}, rip[ADDR_LEN] = {0,};
    iaddr laddr, raddr;
    unsigned lport, rport, state, txq, rxq, num, uid;
    unsigned long inode;

    int nitems = sscanf(toybuf, " %d: %x:%x %x:%x %x %x:%x %*X:%*X %*X %d %*d %ld",
                        &num, &laddr.u, &lport, &raddr.u, &rport, &state, &txq,
                        &rxq, &uid, &inode);
    if (nitems == 10) {
      addr2str(AF_INET, &laddr, lport, lip, label);
      addr2str(AF_INET, &raddr, rport, rip, label);
      show_data(rport, label, rxq, txq, lip, rip, state, uid, inode);
    }
  }//End of While
  fclose(fp);
}

/*
 * display ipv6 info for TCP/UDP/RAW.
 */
static void show_ipv6(char *fname, char *label)
{
  FILE *fp = fopen(fname, "r");
  if (!fp) {
    perror_msg("'%s'", fname);
    return;
  }

  if(!fgets(toybuf, sizeof(toybuf), fp)) return; //skip header.

  while (fgets(toybuf, sizeof(toybuf), fp)) {
    char lip[ADDR_LEN] = {0,}, rip[ADDR_LEN] = {0,};
    iaddr6 laddr6, raddr6;
    unsigned lport, rport, state, txq, rxq, num, uid;
    unsigned long inode;
    int nitems = sscanf(toybuf, " %d: %8x%8x%8x%8x:%x %8x%8x%8x%8x:%x %x %x:%x "
                                "%*X:%*X %*X %d %*d %ld",
                        &num, &laddr6.u.a, &laddr6.u.b, &laddr6.u.c,
                        &laddr6.u.d, &lport, &raddr6.u.a, &raddr6.u.b,
                        &raddr6.u.c, &raddr6.u.d, &rport, &state, &txq, &rxq,
                        &uid, &inode);
    if (nitems == 16) {
      addr2str(AF_INET6, &laddr6, lport, lip, label);
      addr2str(AF_INET6, &raddr6, rport, rip, label);
      show_data(rport, label, rxq, txq, lip, rip, state, uid, inode);
    }
  }//End of While
  fclose(fp);
}

/*
 * display unix socket info.
 */
static void show_unix_sockets(char *fname, char *label)
{
  FILE *fp = fopen((char *)fname, "r");
  if (!fp) {
    perror_msg("'%s'", fname);
    return;
  }

  if(!fgets(toybuf, sizeof(toybuf), fp)) return; //skip header.

  while (fgets(toybuf, sizeof(toybuf), fp)) {
    unsigned long refcount, label, flags, inode;
    int nitems = 0, path_offset = 0, type, state;
    char sock_flags[32] = {0,}, *sock_type, *sock_state, *bptr = toybuf, *term;

    if (!toybuf[0]) continue;

    nitems = sscanf(toybuf, "%*p: %lX %lX %lX %X %X %lu %n",
        &refcount, &label, &flags, &type, &state, &inode, &path_offset);

    //for state one less
    if (nitems < 6) break;

    if (toys.optflags & FLAG_l) {
      if ( !((state == SOCK_NOT_CONNECTED) && (flags & SOCK_ACCEPTCON)) )
        continue;
    } else if (!(toys.optflags & FLAG_a)) {
      if ((state == SOCK_NOT_CONNECTED) && (flags & SOCK_ACCEPTCON)) continue;
    }

    //prepare socket type, state and flags.
    {
      char *ss_type[] = { "", "STREAM", "DGRAM", "RAW", "RDM", "SEQPACKET",
                          "UNKNOWN"};
      char *ss_state[] = { "FREE", "LISTENING", "CONNECTING", "CONNECTED",
                           "DISCONNECTING", "UNKNOWN"};

      int sz = ARRAY_LEN(ss_type);//sizeof(ss_type)/sizeof(ss_type[0]);
      if ( (type < SOCK_STREAM) || (type > SOCK_SEQPACKET) )
        sock_type = ss_type[sz-1];
      else sock_type = ss_type[type];

      sz = ARRAY_LEN(ss_state);//sizeof(ss_state)/sizeof(ss_state[0]);
      if ((state < 0) || (state > sz-2)) sock_state = ss_state[sz-1];
      else if (state == SOCK_NOT_CONNECTED) {
        if (flags & SOCK_ACCEPTCON) sock_state = ss_state[state];
        else sock_state = " ";
      } else sock_state = ss_state[state];

      strcpy(sock_flags, "[ ");
      if (flags & SOCK_ACCEPTCON) strcat(sock_flags, "ACC ");
      if (flags & SOCK_WAIT_DATA) strcat(sock_flags, "W ");
      if (flags & SOCK_NO_SPACE) strcat(sock_flags, "N ");
      strcat(sock_flags, "]");
    }
    xprintf("%-5s %-6ld %-11s %-10s %-13s %8lu ", (!label ? "unix" : "??"),
      refcount, sock_flags, sock_type, sock_state, inode);
    if (toys.optflags & FLAG_p) xprintf("%-20s", get_pid_name(inode));

    bptr += path_offset;
    if ((term = strchr(bptr, '\n'))) *term = '\0';
    xprintf("%s\n", bptr);
  }//End of while
  fclose(fp);
}

/*
 * extract inode value from the link.
 */
static long ss_inode(char *link)
{
  long inode = -1;
  //"link = socket:[12345]", get "12345" as inode.
  if (!strncmp(link, "socket:[", sizeof("socket:[")-1)) {
    inode = get_strtou(link + sizeof("socket:[")-1, (char**)&link, 0);
    if (*link != ']') inode = -1;
  }
  //"link = [0000]:12345", get "12345" as inode.
  else if (!strncmp(link, "[0000]:", sizeof("[0000]:")-1)) {
    inode = get_strtou(link + sizeof("[0000]:")-1, NULL, 0);
    //if not NULL terminated.
    if (errno) inode = -1;
  }
  return inode;
}

/*
 * add inode and progname in the pid list.
 */
static void add2list(long inode)
{
  PID_LIST *node = pid_list;

  for(; node; node = node->next) {
    if(node->inode == inode)
      return;
  }

  PID_LIST *new = (PID_LIST *)xzalloc(sizeof(PID_LIST));
  new->inode = inode;
  xstrncpy(new->name, TT.current_name, sizeof(new->name));
  new->next = pid_list;
  pid_list = new;
}

static void scan_pid_inodes(char *path)
{
  DIR *dp;
  struct dirent *entry;

  if (!(dp = opendir(path))) {
    if (errno == EACCES) {
      TT.some_process_unidentified = 1;
      return;
    } else perror_exit("%s", path);
  }
  while ((entry = readdir(dp))) {
    char link_name[64], *link;
    long inode;

    if (!isdigit(entry->d_name[0])) continue;
    snprintf(link_name, sizeof(link_name), "%s/%s", path, entry->d_name);
    if ((link = xreadlink(link_name)) && (inode = ss_inode(link))!=-1)
      add2list(inode);
    free(link);
  }
  closedir(dp);
}

static void scan_pid(int pid)
{
  char *line, *p, *fd_dir;

  snprintf(toybuf, sizeof(toybuf), "/proc/%d/cmdline", pid);
  line = xreadfile(toybuf, 0, 0);

  if ((p = strchr(line, ' '))) *p = 0; // "/bin/netstat -ntp" -> "/bin/netstat"
  snprintf(TT.current_name, sizeof(TT.current_name), "%d/%s",
           pid, getbasename(line)); // "584/netstat"
  free(line);

  fd_dir = xmprintf("/proc/%d/fd", pid);
  scan_pid_inodes(fd_dir);
  free(fd_dir);
}

static int scan_pids(struct dirtree *node)
{
  int pid;

  if (!node->parent) return DIRTREE_RECURSE;
  if ((pid = atol(node->name))) scan_pid(pid);

  return 0;
}

/*
 * Dealloc pid list.
 */
static void clean_pid_list(void)
{
  PID_LIST *tmp;
  while (pid_list) {
    tmp = pid_list->next;
    free(pid_list);
    pid_list = tmp;
  }
}

/*
 * For TCP/UDP/RAW show the header.
 */
static void show_header(void)
{
  xprintf("Proto Recv-Q Send-Q ");
  xprintf((toys.optflags & FLAG_W) ? "%-51s %-51s" : "%-23s %-23s",
          "Local Address", "Foreign Address");
  xprintf(" State      ");
  if (toys.optflags & FLAG_e) xprintf(" User       Inode      ");
  if (toys.optflags & FLAG_p) xprintf(" PID/Program Name");
  xputc('\n');
}

/*
 * used to get the flag values for route command.
 */
static void get_flag_value(char *flagstr, int flags)
{
  int i = 0;
  char *str = flagstr;
  static const char flagchars[] = "GHRDMDAC";
  static const unsigned flagarray[] = {
    RTF_GATEWAY,
    RTF_HOST,
    RTF_REINSTATE,
    RTF_DYNAMIC,
    RTF_MODIFIED,
    RTF_DEFAULT,
    RTF_ADDRCONF,
    RTF_CACHE
  };
  *str++ = 'U';

  while ( (*str = flagchars[i]) ) {
    if (flags & flagarray[i++]) ++str;
  }
}

/*
 * extract inet4 route info from /proc/net/route file and display it.
 */
static void display_routes(int is_more_info, int notresolve)
{
#define IPV4_MASK (RTF_GATEWAY|RTF_HOST|RTF_REINSTATE|RTF_DYNAMIC|RTF_MODIFIED)
  unsigned long dest, gate, mask;
  int flags, ref, use, metric, mss, win, irtt;
  char iface[64]={0,};
  char flag_val[10]={0,}; //there are 9 flags "UGHRDMDAC" for route.

  FILE *fp = xfopen("/proc/net/route", "r");

  if(!fgets(toybuf, sizeof(toybuf), fp)) return; //skip header.

  xprintf("Kernel IP routing table\n"
          "Destination     Gateway         Genmask         Flags %s Iface\n",
          is_more_info ? "  MSS Window  irtt" : "Metric Ref    Use");

  while (fgets(toybuf, sizeof(toybuf), fp)) {
     int nitems = 0;
     char *destip = NULL, *gateip = NULL, *maskip = NULL;

     nitems = sscanf(toybuf, "%63s%lx%lx%X%d%d%d%lx%d%d%d\n", iface, &dest,
       &gate, &flags, &ref, &use, &metric, &mask, &mss, &win, &irtt);
     if (nitems != 11) {//EOF with no (nonspace) chars read.
       if ((nitems < 0) && feof(fp)) break;
      perror_exit("sscanf");
    }

    //skip down interfaces.
    if (!(flags & RTF_UP)) continue;

    if (dest) {//For Destination
      if (inet_ntop(AF_INET, &dest, toybuf, sizeof(toybuf)) )
        destip = xstrdup(toybuf);
    } else {
      if (!notresolve) destip = xstrdup("default");
      else destip = xstrdup("0.0.0.0");
    }

    if (gate) {//For Gateway
      if (inet_ntop(AF_INET, &gate, toybuf, sizeof(toybuf)) )
        gateip = xstrdup(toybuf);
    } else {
      if (!notresolve) gateip = xstrdup("*");
      else gateip = xstrdup("0.0.0.0");
    }

    //For Mask
    if (inet_ntop(AF_INET, &mask, toybuf, sizeof(toybuf)) )
      maskip = xstrdup(toybuf);

    //Get flag Values
    get_flag_value(flag_val, flags & IPV4_MASK);
    if (flags & RTF_REJECT) flag_val[0] = '!';

    xprintf("%-15.15s %-15.15s %-16s%-6s", destip, gateip, maskip, flag_val);
    if (is_more_info) xprintf("%5d %-5d %6d %s\n", mss, win, irtt, iface);
    else xprintf("%-6d %-2d %7d %s\n", metric, ref, use, iface);

    if (destip) free(destip);
    if (gateip) free(gateip);
    if (maskip) free(maskip);
  }//end of while.
  fclose(fp);
#undef IPV4_MASK
}

/*
 * netstat utility main function.
 */
void netstat_main(void)
{
#define IS_NETSTAT_PROTO_FLAGS_UP (toys.optflags & (FLAG_t | FLAG_u | FLAG_w \
                                                    | FLAG_x))

  // For no parameter, add 't', 'u', 'w', 'x' options as default
  if (!toys.optflags) toys.optflags = FLAG_t | FLAG_u | FLAG_w | FLAG_x;

  // For both 'a' and 'l' are set, remove 'l' option
  if (toys.optflags & FLAG_a && toys.optflags & FLAG_l)
      toys.optflags &= ~FLAG_l;

  // For each 'a', 'l', 'e', 'n', 'W', 'p' options
  // without any 't', 'u', 'w', 'x' option, add 't', 'u', 'w', 'x' options
  if (((toys.optflags & FLAG_a) || (toys.optflags & FLAG_l) ||
       (toys.optflags & FLAG_e) || (toys.optflags & FLAG_n) ||
       (toys.optflags & FLAG_W) || (toys.optflags & FLAG_p)) &&
         (!IS_NETSTAT_PROTO_FLAGS_UP) )
    toys.optflags |= FLAG_t | FLAG_u | FLAG_w | FLAG_x;

  //Display routing table.
  if (toys.optflags & FLAG_r) {
    display_routes(!(toys.optflags & FLAG_e), (toys.optflags & FLAG_n));
    return;
  }

  if (toys.optflags & FLAG_p) {
    dirtree_read("/proc", scan_pids);
    // TODO: we probably shouldn't warn if all the processes we're going to
    // list were identified.
    if (TT.some_process_unidentified)
      fprintf(stderr,
        "(Not all processes could be identified, non-owned process info\n"
        " will not be shown, you would have to be root to see it all.)\n");
  }

  //For TCP/UDP/RAW.
  if ( (toys.optflags & FLAG_t) || (toys.optflags & FLAG_u) ||
       (toys.optflags & FLAG_w) ) {
    xprintf("Active Internet connections ");

    if (toys.optflags & FLAG_a) xprintf("(servers and established)\n");
    else if (toys.optflags & FLAG_l) xprintf("(only servers)\n");
    else xprintf("(w/o servers)\n");

    show_header();
    if (toys.optflags & FLAG_t) {//For TCP
      show_ipv4("/proc/net/tcp",  "tcp");
      show_ipv6("/proc/net/tcp6", "tcp");
    }
    if (toys.optflags & FLAG_u) {//For UDP
      show_ipv4("/proc/net/udp",  "udp");
      show_ipv6("/proc/net/udp6", "udp");
    }
    if (toys.optflags & FLAG_w) {//For raw
      show_ipv4("/proc/net/raw",  "raw");
      show_ipv6("/proc/net/raw6", "raw");
    }
  }
  if (toys.optflags & FLAG_x) {//For UNIX
    xprintf("Active UNIX domain sockets ");
    if (toys.optflags & FLAG_a) xprintf("(servers and established)\n");
    else if (toys.optflags & FLAG_l) xprintf("(only servers)\n");
    else xprintf("(w/o servers)\n");

    if (toys.optflags & FLAG_p)
      xprintf("Proto RefCnt Flags       Type       State           "
              "I-Node PID/Program Name    Path\n");
    else
      xprintf("Proto RefCnt Flags       Type       State           "
              "I-Node Path\n");
    show_unix_sockets("/proc/net/unix", "unix");
  }
  if (toys.optflags & FLAG_p) clean_pid_list();
  if (toys.exitval) toys.exitval = 0;
#undef IS_NETSTAT_PROTO_FLAGS_UP
}