Implemented netlink protocol parsing functions. More to come tomorrow.

TODO

@@ -21,8 +21,7 @@ Core
 - broadcast/multicast echoing suppresion
 - we need ifindex at least for PtP links
 
-- kernel: RTM_F_NOTIFY seems to be unimplemented
-- kernel: RTM_DELROUTE not announced for device routes
+- kernel: RTM_DELROUTE not announced for device routes [confirmed by Alexey: it's a feature]
 
 - netlink: import Linux route attributes to our rta's, so that they can be filtered?
 
@@ -35,6 +34,7 @@ Cleanup
 - check log calls for trailing newlines
 - check if all protocols set proper packet priorities and TTL's.
 - replace all NUM's by expr's
+- try compiling with -Wunused
 
 Various ideas
 ~~~~~~~~~~~~~

sysdep/linux/netlink/krt.c

@@ -10,6 +10,11 @@
 #include <stdio.h>
 #include <fcntl.h>
 #include <sys/socket.h>
+#include <sys/uio.h>
+
+#define LOCAL_DEBUG
+
+#undef ASYNC_NETLINK			/* Define if async notifications should be used (debug) */
 
 #include "nest/bird.h"
 #include "nest/route.h"
@@ -18,6 +23,7 @@
 #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,
@@ -35,10 +41,218 @@
 #include <linux/netlink.h>
 #include <linux/rtnetlink.h>
 
-#define LOCAL_DEBUG
+#ifndef MSG_TRUNC			/* FIXME: Hack to circumvent omissions in glibc includes */
+#define MSG_TRUNC 0x20
+#endif
 
 struct proto_config *cf_krt;
 
+/*
+ *	Synchronous Netlink interface
+ */
+
+static int nl_sync_fd;			/* 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_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");
+	  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)
+{
+  struct ifinfomsg *i;
+  struct rtattr *a[IFLA_STATS+1];
+
+  if (!(i = nl_checkin(h, sizeof(*i))) || !nl_parse_attrs(IFLA_RTA(i), a, sizeof(a)))
+    return;
+  DBG("NEWLINK %d\n", i->ifi_index);
+}
+
+static void
+nl_parse_addr(struct nlmsghdr *h)
+{
+  struct ifaddrmsg *i;
+  struct rtattr *a[IFA_ANYCAST+1];
+
+  if (!(i = nl_checkin(h, sizeof(*i))) || !nl_parse_attrs(IFA_RTA(i), a, sizeof(a)))
+    return;
+  DBG("NEWADDR %d\n", i->ifa_index);
+}
+
+static void
+nl_scan_ifaces(void)
+{
+  struct nlmsghdr *h;
+
+  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);
+    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);
+
+  bug("NIIDW");
+}
+
+/*
+ *	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;
+}
+
+/*
+ *	Protocol core
+ */
+
 static void
 krt_preconfig(struct protocol *x, struct config *c)
 {
@@ -56,9 +270,33 @@ krt_init(struct proto_config *c)
   return &p->p;
 }
 
+static void
+nl_open_async(struct proto *p)
+{
+  sock *sk;
+  struct sockaddr_nl sa;
+
+  sk = nl_async_sk = sk_new(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");
+}
+
 static int
 krt_start(struct proto *p)
 {
+#ifdef ASYNC_NETLINK
+  nl_open_async(p);
+#endif
+
   /* FIXME: Filter kernel routing table etc. */
 
   return PS_UP;
@@ -75,7 +313,14 @@ krt_shutdown(struct proto *p)
 void
 scan_if_init(void)
 {
-  /* FIXME: What to do here? */
+  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);
+  /* FIXME: Should we fetch our local address and compare it with addresses of all incoming messages? */
+
+  nl_scan_ifaces();
 }
 
 struct protocol proto_unix_kernel = {