/* route.c - Display/edit network routing table.
 *
 * Copyright 2012 Ranjan Kumar <ranjankumar.bth@gmail.com>
 * Copyright 2013 Kyungwan Han <asura321@gmail.com>
 * Copyright 2020 Eric Molitor <eric@molitor.org>
 *
 * No Standard
 *
 * route add -net target 10.0.0.0 netmask 255.0.0.0 dev eth0
 * route del delete
 * delete net route, must match netmask, informative error message
 *
 * mod dyn reinstate metric netmask gw mss window irtt dev

USE_ROUTE(NEWTOY(route, "?neA:", TOYFLAG_SBIN))
config ROUTE
  bool "route"
  default n
  help
    usage: route [-ne] [-A [inet|inet6]] [add|del TARGET [OPTIONS]]

    Display, add or delete network routes in the "Forwarding Information Base".

    -n	Show numerical addresses (no DNS lookups)
    -e	display netstat fields

    Routing means sending packets out a network interface to an address.
    The kernel can tell where to send packets one hop away by examining each
    interface's address and netmask, so the most common use of this command
    is to identify a "gateway" that forwards other traffic.

    Assigning an address to an interface automatically creates an appropriate
    network route ("ifconfig eth0 10.0.2.15/8" does "route add 10.0.0.0/8 eth0"
    for you), although some devices (such as loopback) won't show it in the
    table. For machines more than one hop away, you need to specify a gateway
    (ala "route add default gw 10.0.2.2").

    The address "default" is a wildcard address (0.0.0.0/0) matching all
    packets without a more specific route.

    Available OPTIONS include:
    reject   - blocking route (force match failure)
    dev NAME - force packets out this interface (ala "eth0")
    netmask  - old way of saying things like ADDR/24
    gw ADDR  - forward packets to gateway ADDR

*/

#define FOR_route
#include "toys.h"
#define _LINUX_SYSINFO_H     // workaround for musl bug
#include <linux/rtnetlink.h>

GLOBALS(
  char *family;
)

struct _arglist {
  char *arg;
  int action;
};

static struct _arglist arglist1[] = {
  { "add", 1 }, { "del", 2 },
  { "delete", 2 }, { NULL, 0 }
};

static struct _arglist arglist2[] = {
  { "-net", 1 }, { "-host", 2 },
  { NULL, 0 }
};

void xsend(int sockfd, void *buf, size_t len)
{
  if (send(sockfd, buf, len, 0) != len) perror_exit("xsend");
}

int xrecv(int sockfd, void *buf, size_t len)
{
  int msg_len = recv(sockfd, buf, len, 0);
  if (msg_len < 0) perror_exit("xrecv");

  return msg_len;
}

void addAttr(struct nlmsghdr *nl, int maxlen, void *attr, int type, int len)
{
  struct rtattr *rt;
  int rtlen = RTA_LENGTH(len);
  if (NLMSG_ALIGN(nl->nlmsg_len) + rtlen > maxlen) perror_exit("addAttr");
  rt = (struct rtattr*)((char *)nl + NLMSG_ALIGN(nl->nlmsg_len));
  rt->rta_type = type;
  rt->rta_len = rtlen;
  memcpy(RTA_DATA(rt), attr, len);
  nl->nlmsg_len = NLMSG_ALIGN(nl->nlmsg_len) + rtlen;
}

static void get_hostname(sa_family_t f, void *a, char *dst, size_t len) {
  size_t a_len = (AF_INET6 == f) ? sizeof(struct in6_addr) : sizeof(struct in_addr);

  struct hostent *host = gethostbyaddr(a, a_len, f);
  if (host) xstrncpy(dst, host->h_name, len);
}

static void display_routes(sa_family_t f)
{
  int fd, msg_hdr_len, route_protocol;
  struct {
    struct nlmsghdr nl;
    struct rtmsg rt;
  } req;
  struct nlmsghdr buf[8192 / sizeof(struct nlmsghdr)];
  struct nlmsghdr *msg_hdr_ptr;
  struct rtmsg *route_entry;
  struct rtattr *route_attribute;

  fd = xsocket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);

  memset(&req, 0, sizeof(req));
  req.nl.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
  req.nl.nlmsg_type = RTM_GETROUTE;
  req.nl.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
  req.nl.nlmsg_pid = getpid();
  req.nl.nlmsg_seq = 1;
  req.rt.rtm_family = f;
  req.rt.rtm_table = RT_TABLE_MAIN;
  xsend(fd, &req, sizeof(req));

  if (f == AF_INET) {
    xprintf("Kernel IP routing table\n"
            "Destination     Gateway         Genmask         Flags %s Iface\n",
            (toys.optflags & FLAG_e) ? "  MSS Window  irtt" : "Metric Ref    Use");
  } else {
    xprintf("Kernel IPv6 routing table\n"
            "%-31s%-26s Flag Metric Ref Use If\n", "Destination", "Next Hop");
  }

  msg_hdr_len = xrecv(fd, buf, sizeof(buf));
  msg_hdr_ptr = buf;
  while (msg_hdr_ptr->nlmsg_type != NLMSG_DONE) {
    while (NLMSG_OK(msg_hdr_ptr, msg_hdr_len)) {
      route_entry = NLMSG_DATA(msg_hdr_ptr);
      route_protocol = route_entry->rtm_protocol;

      // Annoyingly NLM_F_MATCH is not yet implemented so even if we pass in
      // RT_TABLE_MAIN with RTM_GETROUTE it still returns everything so we
      // have to filter here.
      if (route_entry->rtm_table == RT_TABLE_MAIN) {
        struct in_addr netmask_addr;
        char dest[INET6_ADDRSTRLEN];
        char gate[INET6_ADDRSTRLEN];
        char netmask[32];
        char flags[10] = "U";
        uint32_t priority = 0;
        uint32_t mss = 0;
        uint32_t win = 0;
        uint32_t irtt = 0;
        uint32_t ref = 0;
        uint32_t use = 0;
        char if_name[IF_NAMESIZE] = "-";
        uint32_t route_netmask;
        struct rtattr *metric;
        uint32_t metric_len;
        struct rta_cacheinfo *cache_info;

        if (f == AF_INET) {
          if (!(toys.optflags & FLAG_n)) strcpy(dest, "default");
          else strcpy(dest, "0.0.0.0");
          if (!(toys.optflags & FLAG_n)) strcpy(gate, "*");
          else strcpy(gate, "0.0.0.0");
          strcpy(netmask, "0.0.0.0");
        } else {
          strcpy(dest, "::");
          strcpy(gate, "::");
        }

        route_netmask = route_entry->rtm_dst_len;
        if (route_netmask == 0) {
          netmask_addr.s_addr = ~((in_addr_t) -1);
        } else {
          netmask_addr.s_addr = htonl(~((1 << (32 - route_netmask)) - 1));
        }
        inet_ntop(AF_INET, &netmask_addr, netmask, sizeof(netmask));

        route_attribute = RTM_RTA(route_entry);
        int route_attribute_len = RTM_PAYLOAD(msg_hdr_ptr);
        while (RTA_OK(route_attribute, route_attribute_len)) {
          switch (route_attribute->rta_type) {
            case RTA_DST:
              if (toys.optflags & FLAG_n) {
                inet_ntop(f, RTA_DATA(route_attribute), dest, sizeof(dest));
              } else {
                get_hostname(f, RTA_DATA(route_attribute), dest, sizeof(dest));
              }
              break;

            case RTA_GATEWAY:
              if (toys.optflags & FLAG_n) {
                inet_ntop(f, RTA_DATA(route_attribute), gate, sizeof(dest));
              } else {
                get_hostname(f, RTA_DATA(route_attribute), gate, sizeof(dest));
              }
              strcat(flags, "G");
              break;

            case RTA_PRIORITY:
              priority = *(uint32_t *) RTA_DATA(route_attribute);
              break;

            case RTA_OIF:
              if_indextoname(*((int *) RTA_DATA(route_attribute)), if_name);
              break;

            case RTA_METRICS:
              metric_len = RTA_PAYLOAD(route_attribute);
              for (metric = RTA_DATA(route_attribute);
                   RTA_OK(metric, metric_len);
                   metric=RTA_NEXT(metric, metric_len)) {
                if (metric->rta_type == RTAX_ADVMSS) {
                  mss = *(uint32_t *) RTA_DATA(metric);
                } else if (metric->rta_type == RTAX_WINDOW) {
                  win = *(uint32_t *) RTA_DATA(metric);
                } else if (metric->rta_type == RTAX_RTT) {
                  irtt = (*(uint32_t *) RTA_DATA(metric)) / 8;
                }
              }
              break;

            case RTA_CACHEINFO:
              cache_info = RTA_DATA(route_attribute);
              ref = cache_info->rta_clntref;
              use = cache_info->rta_used;
              break;
          }

          route_attribute = RTA_NEXT(route_attribute, route_attribute_len);
        }

        if (route_entry->rtm_type == RTN_UNREACHABLE) flags[0] = '!';
        if (route_netmask == 32) strcat(flags, "H");
        if (route_protocol == RTPROT_REDIRECT) strcat(flags, "D");

        if (f == AF_INET) {
          xprintf("%-15.15s %-15.15s %-16s%-6s", dest, gate, netmask, flags);
          if (toys.optflags & FLAG_e) {
            xprintf("%5d %-5d %6d %s\n", mss, win, irtt, if_name);
          } else xprintf("%-6d %-2d %7d %s\n", priority, ref, use, if_name);
        } else {
          char *dest_with_mask = xmprintf("%s/%u", dest, route_netmask);
          xprintf("%-30s %-26s %-4s %-6d %-4d %2d %-8s\n",
                  dest_with_mask, gate, flags, priority, ref, use, if_name);
          free(dest_with_mask);
        }
      }
      msg_hdr_ptr = NLMSG_NEXT(msg_hdr_ptr, msg_hdr_len);
    }

    msg_hdr_len = xrecv(fd, buf, sizeof(buf));
    msg_hdr_ptr = buf;
  }

  xclose(fd);
}

/*
 * find the given parameter in list like add/del/net/host.
 * and if match found return the appropriate action.
 */
static int get_action(char ***argv, struct _arglist *list)
{
  struct _arglist *alist;

  if (!**argv) return 0;
  for (alist = list; alist->arg; alist++) { //find the given parameter in list
    if (!strcmp(**argv, alist->arg)) {
      *argv += 1;
      return alist->action;
    }
  }
  return 0;
}

// add/del a route.
static void setroute(sa_family_t f, char **argv)
{
  char *targetip;
  int sockfd, arg2_action;
  int action = get_action(&argv, arglist1); //verify the arg for add/del.
  struct nlmsghdr buf[8192 / sizeof(struct nlmsghdr)];
  struct nlmsghdr *nlMsg;
  struct rtmsg *rtMsg;

  if (!action || !*argv) help_exit("setroute");
  arg2_action = get_action(&argv, arglist2); //verify the arg for -net or -host
  if (!*argv) help_exit("setroute");
  targetip = *argv++;
  sockfd = xsocket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
  memset(buf, 0, sizeof(buf));
  nlMsg = (struct nlmsghdr *) buf;
  rtMsg = (struct rtmsg *) NLMSG_DATA(nlMsg);

  nlMsg->nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));

  //TODO(emolitor): Improve action and arg2_action handling
  if (action == 1) { // Add
    nlMsg->nlmsg_type = RTM_NEWROUTE;
    nlMsg->nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
  } else { // Delete
    nlMsg->nlmsg_type = RTM_DELROUTE;
    nlMsg->nlmsg_flags = NLM_F_REQUEST;
  }

  nlMsg->nlmsg_pid = getpid();
  nlMsg->nlmsg_seq = 1;
  rtMsg->rtm_family = f;
  rtMsg->rtm_table = RT_TABLE_UNSPEC;
  rtMsg->rtm_type = RTN_UNICAST;
  rtMsg->rtm_protocol = RTPROT_UNSPEC;
  rtMsg->rtm_flags = RTM_F_NOTIFY;
  if (f == AF_INET) {
    rtMsg->rtm_dst_len = 32;
    rtMsg->rtm_src_len = 32;
  } else {
    rtMsg->rtm_dst_len = 128;
    rtMsg->rtm_src_len = 128;
  }

  if (arg2_action == 2) {
    rtMsg->rtm_scope = RT_SCOPE_HOST;
  }

  size_t addr_len = sizeof(struct in_addr);
  if (f == AF_INET6) addr_len = sizeof(struct in6_addr);
  unsigned char addr[sizeof(struct in6_addr)] = {0,};

  for (; *argv; argv++) {
    if (!strcmp(*argv, "mod")) {
      continue;
    } else if (!strcmp(*argv, "dyn")) {
      continue;
    } else if (!strcmp(*argv, "reinstate")) {
      continue;
    } else if (!strcmp(*argv, "reject")) {
      rtMsg->rtm_type = RTN_UNREACHABLE;
    } else {
      if (!argv[1]) show_help(stdout, 1);

      if (!strcmp(*argv, "metric")) {
        unsigned int priority = atolx_range(argv[1], 0, UINT_MAX);
        addAttr(nlMsg, sizeof(toybuf), &priority, RTA_PRIORITY, sizeof(unsigned int));
      } else if (!strcmp(*argv, "netmask")) {
        uint32_t netmask;
        char *ptr;
        uint32_t naddr[4] = {0,};
        uint64_t plen;

        netmask = (f == AF_INET6) ? 128 : 32; // set default netmask
        plen = strtoul(argv[1], &ptr, 0);

        if (!ptr || ptr == argv[1] || *ptr || !plen || plen > netmask) {
          if (!inet_pton(f, argv[1], &naddr)) error_exit("invalid netmask");
          if (f == AF_INET) {
            uint32_t mask = htonl(*naddr), host = ~mask;
            if (host & (host + 1)) error_exit("invalid netmask");
            for (plen = 0; mask; mask <<= 1) ++plen;
            if (plen > 32) error_exit("invalid netmask");
          }
        }
        netmask = plen;
        rtMsg->rtm_dst_len = netmask;
      } else if (!strcmp(*argv, "gw")) {
        if (!inet_pton(f, argv[1], &addr)) error_exit("invalid gw");
        addAttr(nlMsg, sizeof(toybuf), &addr, RTA_GATEWAY, addr_len);
      } else if (!strcmp(*argv, "mss")) {
        // TODO(emolitor): Add RTA_METRICS support
        //set the TCP Maximum Segment Size for connections over this route.
        //rt->rt_mtu = atolx_range(argv[1], 64, 65536);
        //rt->rt_flags |= RTF_MSS;
      } else if (!strcmp(*argv, "window")) {
        // TODO(emolitor): Add RTA_METRICS support
        //set the TCP window size for connections over this route to W bytes.
        //rt->rt_window = atolx_range(argv[1], 128, INT_MAX); //win low
        //rt->rt_flags |= RTF_WINDOW;
      } else if (!strcmp(*argv, "irtt")) {
        // TODO(emolitor): Add RTA_METRICS support
        //rt->rt_irtt = atolx_range(argv[1], 0, INT_MAX);
        //rt->rt_flags |= RTF_IRTT;
      } else if (!strcmp(*argv, "dev")) {
        unsigned int if_idx = if_nametoindex(argv[1]);
        if (!if_idx) perror_exit("dev");
        addAttr(nlMsg, sizeof(toybuf), &if_idx, RTA_OIF, sizeof(unsigned int));
      } else help_exit("no '%s'", *argv);
      argv++;
    }
  }

  if (strcmp(targetip, "default") != 0) {
    char *ptr;
    char *dst = strtok(targetip, "/");
    char *prefix = strtok(NULL, "/");

    if (prefix) rtMsg->rtm_dst_len = strtoul(prefix, &ptr, 0);
    if (!inet_pton(f, dst, &addr)) error_exit("invalid target");
    addAttr(nlMsg, sizeof(toybuf), &addr, RTA_DST, addr_len);
  } else {
    rtMsg->rtm_dst_len = 0;
  }

  xsend(sockfd, nlMsg, nlMsg->nlmsg_len);
  xclose(sockfd);
}

void route_main(void)
{
  if (!*toys.optargs) {
    if ( (!TT.family) || (!strcmp(TT.family, "inet")) ) display_routes(AF_INET);
    else if (!strcmp(TT.family, "inet6")) display_routes(AF_INET6);
    else show_help(stdout, 1);
  } else {
    if (!TT.family) {
      if ( (toys.optc > 1) && (strchr(toys.optargs[1], ':')) ) {
          xprintf("WARNING: Implicit IPV6 address using -Ainet6\n");
          TT.family = "inet6";
      } else TT.family = "inet";
    }

    if (!strcmp(TT.family, "inet")) setroute(AF_INET, toys.optargs);
    else setroute(AF_INET6, toys.optargs);
  }
}