Rewrote the kernel syncer. The old layering was horrible.

The new kernel syncer is cleanly split between generic UNIX module
and OS dependent submodules:

  -  krt.c (the generic part)
  -  krt-iface (low-level functions for interface handling)
  -  krt-scan (low-level functions for routing table scanning)
  -  krt-set (low-level functions for setting of kernel routes)

krt-set and krt-iface are common for all BSD-like Unices, krt-scan is heavily
system dependent (most Unices require /dev/kmem parsing, Linux uses /proc),
Netlink substitues all three modules.

We expect each UNIX port supports kernel routing table scanning, kernel
interface table scanning, kernel route manipulation and possibly also
asynchronous event notifications (new route, interface state change;
not implemented yet) and build the KRT protocol on the top of these
primitive operations.

1 files changed, 440 insertions, 0 deletions

diff --git a/sysdep/linux/netlink/netlink.c b/sysdep/linux/netlink/netlink.c
new file mode 100644
index 00000000..6e6fafd3
--- /dev/null
+++ b/sysdep/linux/netlink/netlink.c
@@ -0,0 +1,440 @@
+/*
+ *	BIRD -- Linux Netlink Interface
+ *
+ *	(c) 1999 Martin Mares <mj@ucw.cz>
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#include <string.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <net/if.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+
+#define LOCAL_DEBUG
+
+#include "nest/bird.h"
+#include "nest/route.h"
+#include "nest/protocol.h"
+#include "nest/iface.h"
+#include "lib/timer.h"
+#include "lib/unix.h"
+#include "lib/krt.h"
+#include "lib/socket.h"
+
+/*
+ *	We need to work around namespace conflicts between us and the kernel,
+ *	but I prefer this way to being forced to rename our configuration symbols.
+ *	This will disappear as soon as netlink headers become part of the libc.
+ */
+
+#undef CONFIG_NETLINK
+#include <linux/config.h>
+#ifndef CONFIG_NETLINK
+#error "Kernel not configured to support netlink"
+#endif
+
+#include <asm/types.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+
+#ifndef MSG_TRUNC			/* FIXME: Hack to circumvent omissions in glibc includes */
+#define MSG_TRUNC 0x20
+#endif
+
+/*
+ *	Synchronous Netlink interface
+ */
+
+static int nl_sync_fd = -1;		/* Unix socket for synchronous netlink actions */
+static u32 nl_sync_seq;			/* Sequence number of last request sent */
+
+static byte *nl_rx_buffer;		/* Receive buffer */
+static int nl_rx_size = 8192;
+
+static struct nlmsghdr *nl_last_hdr;	/* Recently received packet */
+static unsigned int nl_last_size;
+
+static void
+nl_open(void)
+{
+  if (nl_sync_fd < 0)
+    {
+      nl_sync_fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+      if (nl_sync_fd < 0)
+	die("Unable to open rtnetlink socket: %m");
+      nl_sync_seq = now;
+      nl_rx_buffer = xmalloc(nl_rx_size);
+    }
+}
+
+static void
+nl_send(void *rq, int size)
+{
+  struct nlmsghdr *nh = rq;
+  struct sockaddr_nl sa;
+
+  memset(&sa, 0, sizeof(sa));
+  sa.nl_family = AF_NETLINK;
+  nh->nlmsg_len = size;
+  nh->nlmsg_pid = 0;
+  nh->nlmsg_seq = ++nl_sync_seq;
+  if (sendto(nl_sync_fd, rq, size, 0, (struct sockaddr *)&sa, sizeof(sa)) < 0)
+    die("rtnetlink sendto: %m");
+  nl_last_hdr = NULL;
+}
+
+static void
+nl_request_dump(int cmd)
+{
+  struct {
+    struct nlmsghdr nh;
+    struct rtgenmsg g;
+  } req;
+  req.nh.nlmsg_type = cmd;
+  req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
+  req.g.rtgen_family = PF_INET;
+  nl_send(&req, sizeof(req));
+}
+
+static struct nlmsghdr *
+nl_get_reply(void)
+{
+  for(;;)
+    {
+      if (!nl_last_hdr)
+	{
+	  struct iovec iov = { nl_rx_buffer, nl_rx_size };
+	  struct sockaddr_nl sa;
+	  struct msghdr m = { (struct sockaddr *) &sa, sizeof(sa), &iov, 1, NULL, 0, 0 };
+	  int x = recvmsg(nl_sync_fd, &m, 0);
+	  if (x < 0)
+	    die("nl_get_reply: %m");
+	  if (sa.nl_pid)		/* It isn't from the kernel */
+	    {
+	      DBG("Non-kernel packet\n");
+	      continue;
+	    }
+	  nl_last_size = x;
+	  nl_last_hdr = (void *) nl_rx_buffer;
+	  if (m.msg_flags & MSG_TRUNC)
+	    bug("nl_get_reply: got truncated reply which should be impossible");
+	}
+      if (NLMSG_OK(nl_last_hdr, nl_last_size))
+	{
+	  struct nlmsghdr *h = nl_last_hdr;
+	  if (h->nlmsg_seq != nl_sync_seq)
+	    {
+	      log(L_WARN "nl_get_reply: Ignoring out of sequence netlink packet (%x != %x)",
+		  h->nlmsg_seq, nl_sync_seq);
+	      continue;
+	    }
+	  nl_last_hdr = NLMSG_NEXT(h, nl_last_size);
+	  return h;
+	}
+      if (nl_last_size)
+	log(L_WARN "nl_get_reply: Found packet remnant of size %d", nl_last_size);
+      nl_last_hdr = NULL;
+    }
+}
+
+static char *
+nl_error(struct nlmsghdr *h)
+{
+  struct nlmsgerr *e = NLMSG_DATA(h);
+  if (h->nlmsg_len < NLMSG_LENGTH(sizeof(struct nlmsgerr)))
+    return "Error message truncated";
+  else
+    return strerror(-e->error);
+}
+
+static struct nlmsghdr *
+nl_get_scan(void)
+{
+  struct nlmsghdr *h = nl_get_reply();
+
+  if (h->nlmsg_type == NLMSG_DONE)
+    return NULL;
+  if (h->nlmsg_type == NLMSG_ERROR)
+    {
+      log(L_ERR "Netlink error: %s", nl_error(h));
+      return NULL;
+    }
+  return h;
+}
+
+/*
+ *	Parsing of Netlink attributes
+ */
+
+static int nl_attr_len;
+
+static void *
+nl_checkin(struct nlmsghdr *h, int lsize)
+{
+  nl_attr_len = h->nlmsg_len - NLMSG_LENGTH(lsize);
+  if (nl_attr_len < 0)
+    {
+      log(L_ERR "nl_checkin: underrun by %d bytes", -nl_attr_len);
+      return NULL;
+    }
+  return NLMSG_DATA(h);
+}
+
+static int
+nl_parse_attrs(struct rtattr *a, struct rtattr **k, int ksize)
+{
+  int max = ksize / sizeof(struct rtattr *);
+  bzero(k, ksize);
+  while (RTA_OK(a, nl_attr_len))
+    {
+      if (a->rta_type < max)
+	k[a->rta_type] = a;
+      a = RTA_NEXT(a, nl_attr_len);
+    }
+  if (nl_attr_len)
+    {
+      log(L_ERR "nl_parse_attrs: remnant of size %d", nl_attr_len);
+      return 0;
+    }
+  else
+    return 1;
+}
+
+/*
+ *	Scanning of interfaces
+ */
+
+static void
+nl_parse_link(struct nlmsghdr *h, int scan)
+{
+  struct ifinfomsg *i;
+  struct rtattr *a[IFLA_STATS+1];
+  int new = h->nlmsg_type == RTM_NEWLINK;
+  struct iface f;
+  struct iface *ifi;
+  char *name;
+  u32 mtu;
+  unsigned int fl;
+
+  if (!(i = nl_checkin(h, sizeof(*i))) || !nl_parse_attrs(IFLA_RTA(i), a, sizeof(a)))
+    return;
+  if (!a[IFLA_IFNAME] || RTA_PAYLOAD(a[IFLA_IFNAME]) < 2 ||
+      !a[IFLA_MTU] || RTA_PAYLOAD(a[IFLA_MTU]) != 4)
+    {
+      log(L_ERR "nl_parse_link: Malformed message received");
+      return;
+    }
+  name = RTA_DATA(a[IFLA_IFNAME]);
+  memcpy(&mtu, RTA_DATA(a[IFLA_MTU]), sizeof(u32));
+
+  ifi = if_find_by_index(i->ifi_index);
+  if (!new)
+    {
+      DBG("KRT: IF%d(%s) goes down\n", i->ifi_index, name);
+      if (ifi && !scan)
+	{
+	  memcpy(&f, ifi, sizeof(struct iface));
+	  f.flags |= IF_ADMIN_DOWN;
+	  if_update(&f);
+	}
+    }
+  else
+    {
+      DBG("KRT: IF%d(%s) goes up (mtu=%d,flg=%x)\n", i->ifi_index, name, mtu, i->ifi_flags);
+      if (ifi)
+	memcpy(&f, ifi, sizeof(f));
+      else
+	{
+	  bzero(&f, sizeof(f));
+	  f.index = i->ifi_index;
+	}
+      strncpy(f.name, RTA_DATA(a[IFLA_IFNAME]), sizeof(f.name)-1);
+      f.mtu = mtu;
+      f.flags = 0;
+      fl = i->ifi_flags;
+      if (fl & IFF_UP)
+	f.flags |= IF_LINK_UP;
+      if (fl & IFF_POINTOPOINT)
+	f.flags |= IF_UNNUMBERED | IF_MULTICAST;
+      if (fl & IFF_LOOPBACK)
+	f.flags |= IF_LOOPBACK | IF_IGNORE;
+      if (fl & IFF_BROADCAST)
+	f.flags |= IF_BROADCAST | IF_MULTICAST;
+      if_update(&f);
+    }
+}
+
+static void
+nl_parse_addr(struct nlmsghdr *h)
+{
+  struct ifaddrmsg *i;
+  struct rtattr *a[IFA_ANYCAST+1];
+  int new = h->nlmsg_type == RTM_NEWADDR;
+  struct iface f;
+  struct iface *ifi;
+
+  if (!(i = nl_checkin(h, sizeof(*i))) || !nl_parse_attrs(IFA_RTA(i), a, sizeof(a)))
+    return;
+  if (i->ifa_family != AF_INET)
+    return;
+  if (!a[IFA_ADDRESS] || RTA_PAYLOAD(a[IFA_ADDRESS]) != 4 ||
+      !a[IFA_LOCAL] || RTA_PAYLOAD(a[IFA_LOCAL]) != 4 ||
+      (a[IFA_BROADCAST] && RTA_PAYLOAD(a[IFA_BROADCAST]) != 4))
+    {
+      log(L_ERR "nl_parse_addr: Malformed message received");
+      return;
+    }
+  if (i->ifa_flags & IFA_F_SECONDARY)
+    {
+      DBG("KRT: Received address message for secondary address which is not supported.\n"); /* FIXME */
+      return;
+    }
+
+  ifi = if_find_by_index(i->ifa_index);
+  if (!ifi)
+    {
+      log(L_ERR "KRT: Received address message for unknown interface %d\n", i->ifa_index);
+      return;
+    }
+  memcpy(&f, ifi, sizeof(f));
+
+  if (i->ifa_prefixlen > 32 || i->ifa_prefixlen == 31 ||
+      (f.flags & IF_UNNUMBERED) && i->ifa_prefixlen != 32)
+    {
+      log(L_ERR "KRT: Invalid prefix length for interface %s: %d\n", f.name, i->ifa_prefixlen);
+      new = 0;
+    }
+
+  f.ip = f.brd = f.opposite = IPA_NONE;
+  if (!new)
+    {
+      DBG("KRT: IF%d IP address deleted\n");
+      f.pxlen = 0;
+    }
+  else
+    {
+      memcpy(&f.ip, RTA_DATA(a[IFA_LOCAL]), sizeof(f.ip));
+      f.ip = ipa_ntoh(f.ip);
+      f.pxlen = i->ifa_prefixlen;
+      if (f.flags & IF_UNNUMBERED)
+	{
+	  memcpy(&f.opposite, RTA_DATA(a[IFA_ADDRESS]), sizeof(f.opposite));
+	  f.opposite = f.brd = ipa_ntoh(f.opposite);
+	}
+      else if ((f.flags & IF_BROADCAST) && a[IFA_BROADCAST])
+	{
+	  memcpy(&f.brd, RTA_DATA(a[IFA_BROADCAST]), sizeof(f.brd));
+	  f.brd = ipa_ntoh(f.brd);
+	}
+      /* else a NBMA link */
+      f.prefix = ipa_and(f.ip, ipa_mkmask(f.pxlen));
+      DBG("KRT: IF%d IP address set to %I, net %I/%d, brd %I, opp %I\n", f.index, f.ip, f.prefix, f.pxlen, f.brd, f.opposite);
+    }
+  if_update(&f);
+}
+
+void
+krt_if_scan(struct krt_proto *p)
+{
+  struct nlmsghdr *h;
+
+  if_start_update();
+
+  nl_request_dump(RTM_GETLINK);
+  while (h = nl_get_scan())
+    if (h->nlmsg_type == RTM_NEWLINK || h->nlmsg_type == RTM_DELLINK)
+      nl_parse_link(h, 1);
+    else
+      log(L_DEBUG "nl_scan_ifaces: Unknown packet received (type=%d)", h->nlmsg_type);
+
+  nl_request_dump(RTM_GETADDR);
+  while (h = nl_get_scan())
+    if (h->nlmsg_type == RTM_NEWADDR || h->nlmsg_type == RTM_DELADDR)
+      nl_parse_addr(h);
+    else
+      log(L_DEBUG "nl_scan_ifaces: Unknown packet received (type=%d)", h->nlmsg_type);
+
+  if_end_update();
+}
+
+/*
+ *	Routes
+ */
+
+int
+krt_capable(rte *e)
+{
+  return 1;	/* FIXME */
+}
+
+void
+krt_set_notify(struct proto *p, net *n, rte *new, rte *old)
+{
+  /* FIXME */
+}
+
+void
+krt_scan_fire(struct krt_proto *p)
+{
+}
+
+/*
+ *	Asynchronous Netlink interface
+ */
+
+static sock *nl_async_sk;		/* BIRD socket for asynchronous notifications */
+
+static int
+nl_async_hook(sock *sk, int size)
+{
+  DBG("nl_async_hook\n");
+  return 0;
+}
+
+static void
+nl_open_async(struct krt_proto *p)
+{
+  sock *sk;
+  struct sockaddr_nl sa;
+
+  DBG("KRT: Opening async netlink socket\n");
+
+  sk = nl_async_sk = sk_new(p->p.pool);
+  sk->type = SK_MAGIC;
+  sk->rx_hook = nl_async_hook;
+  sk->fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+  if (sk->fd < 0 || sk_open(sk))
+    die("Unable to open secondary rtnetlink socket: %m");
+
+  bzero(&sa, sizeof(sa));
+  sa.nl_family = AF_NETLINK;
+  sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR | RTMGRP_IPV4_ROUTE;
+  if (bind(sk->fd, (struct sockaddr *) &sa, sizeof(sa)) < 0)
+    die("Unable to bind secondary rtnetlink socket: %m");
+}
+
+/*
+ *	Interface to the UNIX krt module
+ */
+
+void
+krt_scan_preconfig(struct krt_config *x)
+{
+  x->scan.async = 1;
+}
+
+void
+krt_scan_start(struct krt_proto *p)
+{
+  nl_open();
+  if (KRT_CF->scan.async)
+    nl_open_async(p);
+}
+
+void
+krt_scan_shutdown(struct krt_proto *p)
+{
+}