rtnl.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2022 Felix Fietkau <nbd@nbd.name>
   4  */
   5 #define _GNU_SOURCE
   6 #include <sys/types.h>
   7 #include <sys/socket.h>
   8 #include <netlink/msg.h>
   9 #include <netlink/attr.h>
  10 #include <netlink/socket.h>
  11 #include <linux/rtnetlink.h>
  12 #include "unetd.h"
  13
  14 static struct nl_sock *rtnl;
  15 bool rtnl_ignore_errors;
  16
  17 static int
  18 unetd_nl_error_cb(struct sockaddr_nl *nla, struct nlmsgerr *err,
  19                    void *arg)
  20 {
  21         struct nlmsghdr *nlh = (struct nlmsghdr *) err - 1;
  22         struct nlattr *tb[NLMSGERR_ATTR_MAX + 1];
  23         struct nlattr *attrs;
  24         int ack_len = sizeof(*nlh) + sizeof(int) + sizeof(*nlh);
  25         int len = nlh->nlmsg_len;
  26         const char *errstr = "(unknown)";
  27
  28         if (rtnl_ignore_errors)
  29                 return NL_STOP;
  30
  31         if (!(nlh->nlmsg_flags & NLM_F_ACK_TLVS))
  32                 return NL_STOP;
  33
  34         if (!(nlh->nlmsg_flags & NLM_F_CAPPED))
  35                 ack_len += err->msg.nlmsg_len - sizeof(*nlh);
  36
  37         attrs = (void *) ((unsigned char *) nlh + ack_len);
  38         len -= ack_len;
  39
  40         nla_parse(tb, NLMSGERR_ATTR_MAX, attrs, len, NULL);
  41         if (tb[NLMSGERR_ATTR_MSG])
  42                 errstr = nla_data(tb[NLMSGERR_ATTR_MSG]);
  43
  44         D("Netlink error(%d): %s\n", err->error, errstr);
  45
  46         return NL_STOP;
  47 }
  48
  49 int rtnl_call(struct nl_msg *msg)
  50 {
  51         int ret;
  52
  53         ret = nl_send_auto_complete(rtnl, msg);
  54         nlmsg_free(msg);
  55
  56         if (ret < 0)
  57                 return ret;
  58
  59         return nl_wait_for_ack(rtnl);
  60 }
  61
  62 int rtnl_init(void)
  63 {
  64         int fd, opt;
  65
  66         if (rtnl)
  67                 return 0;
  68
  69         rtnl = nl_socket_alloc();
  70         if (!rtnl)
  71                 return -1;
  72
  73         if (nl_connect(rtnl, NETLINK_ROUTE))
  74                 goto free;
  75
  76         nl_socket_disable_seq_check(rtnl);
  77         nl_socket_set_buffer_size(rtnl, 65536, 0);
  78         nl_cb_err(nl_socket_get_cb(rtnl), NL_CB_CUSTOM, unetd_nl_error_cb, NULL);
  79
  80         fd = nl_socket_get_fd(rtnl);
  81
  82         opt = 1;
  83         setsockopt(fd, SOL_NETLINK, NETLINK_EXT_ACK, &opt, sizeof(opt));
  84
  85         opt = 1;
  86         setsockopt(fd, SOL_NETLINK, NETLINK_CAP_ACK, &opt, sizeof(opt));
  87
  88         return 0;
  89
  90 free:
  91         nl_socket_free(rtnl);
  92         rtnl = NULL;
  93         return -1;
  94 }