From 714238716ef36f1dfc5721055e2ec4affd42ebfa Mon Sep 17 00:00:00 2001
From: Vincent Bernat <vincent@bernat.ch>
Date: Wed, 10 Feb 2021 16:53:57 +0100
Subject: [PATCH] BGP: Add support for BGP hostname capability

This is an implementation of draft-walton-bgp-hostname-capability-02.
It is implemented since quite some time for FRR and in datacenter, this
gives a nice output to avoid using IP addresses.

It is disabled by default. The hostname is retrieved from uname(2) and
can be overriden with "hostname" option. The domain name is never set
nor displayed.

Minor changes by committer.
---
 conf/conf.c         |  9 +++++++++
 conf/conf.h         |  1 +
 doc/bird.sgml       |  6 ++++++
 nest/cmds.c         |  1 +
 nest/config.Y       |  6 +++++-
 proto/bgp/bgp.c     |  4 ++++
 proto/bgp/bgp.h     |  3 +++
 proto/bgp/config.Y  |  2 ++
 proto/bgp/packets.c | 41 +++++++++++++++++++++++++++++++++++++++++
 sysdep/unix/main.c  | 16 ++++++++++++++++
 sysdep/unix/unix.h  |  1 +
 11 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/conf/conf.c b/conf/conf.c
index 6f64b541..58abcde1 100644
--- a/conf/conf.c
+++ b/conf/conf.c
@@ -55,6 +55,7 @@
 #include "lib/timer.h"
 #include "conf/conf.h"
 #include "filter/filter.h"
+#include "sysdep/unix/unix.h"
 
 
 static jmp_buf conf_jmpbuf;
@@ -217,6 +218,14 @@ config_del_obstacle(struct config *c)
 static int
 global_commit(struct config *new, struct config *old)
 {
+  if (!new->hostname)
+    {
+      new->hostname = get_hostname(new->mem);
+
+      if (!new->hostname)
+        log(L_WARN "Cannot determine hostname");
+    }
+
   if (!old)
     return 0;
 
diff --git a/conf/conf.h b/conf/conf.h
index 3e47c918..860d267a 100644
--- a/conf/conf.h
+++ b/conf/conf.h
@@ -40,6 +40,7 @@ struct config {
   struct timeformat tf_log;		/* Time format for the logfile */
   struct timeformat tf_base;		/* Time format for other purposes */
   u32 gr_wait;				/* Graceful restart wait timeout (sec) */
+  const char *hostname;			/* Hostname */
 
   int cli_debug;			/* Tracing of CLI connections and commands */
   int latency_debug;			/* I/O loop tracks duration of each event */
diff --git a/doc/bird.sgml b/doc/bird.sgml
index 28b0e400..5d1df5bc 100644
--- a/doc/bird.sgml
+++ b/doc/bird.sgml
@@ -585,6 +585,9 @@ include "tablename.conf";;
 	See <ref id="proto-iface" name="interface"> section for detailed
 	description of interface patterns with extended clauses.
 
+	<tag><label id="opt-hostname">hostname "<m/name/"</tag>
+	Set hostname. Default: node name as returned by `uname -n'.
+
 	<tag><label id="opt-graceful-restart">graceful restart wait <m/number/</tag>
 	During graceful restart recovery, BIRD waits for convergence of routing
 	protocols. This option allows to specify a timeout for the recovery to
@@ -2536,6 +2539,9 @@ using the following configuration parameters:
 	This option is relevant to IPv4 mode with enabled capability
 	advertisement only. Default: on.
 
+	<tag><label id="bgp-advertise-hostname">advertise hostname <m/switch/</tag>
+	Advertise hostname capability along with the hostname. Default: off.
+
 	<tag><label id="bgp-disable-after-error">disable after error <m/switch/</tag>
 	When an error is encountered (either locally or by the other side),
 	disable the instance automatically and wait for an administrator to fix
diff --git a/nest/cmds.c b/nest/cmds.c
index da4015cf..18f39eb5 100644
--- a/nest/cmds.c
+++ b/nest/cmds.c
@@ -27,6 +27,7 @@ cmd_show_status(void)
   cli_msg(-1000, "BIRD " BIRD_VERSION);
   tm_format_time(tim, &config->tf_base, current_time());
   cli_msg(-1011, "Router ID is %R", config->router_id);
+  cli_msg(-1011, "Hostname is %s", config->hostname);
   cli_msg(-1011, "Current server time is %s", tim);
   tm_format_time(tim, &config->tf_base, boot_time);
   cli_msg(-1011, "Last reboot on %s", tim);
diff --git a/nest/config.Y b/nest/config.Y
index 0bb8ca51..39bf6149 100644
--- a/nest/config.Y
+++ b/nest/config.Y
@@ -87,7 +87,7 @@ proto_postconfig(void)
 
 CF_DECLS
 
-CF_KEYWORDS(ROUTER, ID, PROTOCOL, TEMPLATE, PREFERENCE, DISABLED, DEBUG, ALL, OFF, DIRECT)
+CF_KEYWORDS(ROUTER, ID, HOSTNAME, PROTOCOL, TEMPLATE, PREFERENCE, DISABLED, DEBUG, ALL, OFF, DIRECT)
 CF_KEYWORDS(INTERFACE, IMPORT, EXPORT, FILTER, NONE, VRF, DEFAULT, TABLE, STATES, ROUTES, FILTERS)
 CF_KEYWORDS(IPV4, IPV6, VPN4, VPN6, ROA4, ROA6, FLOW4, FLOW6, SADR, MPLS)
 CF_KEYWORDS(RECEIVE, LIMIT, ACTION, WARN, BLOCK, RESTART, DISABLE, KEEP, FILTERED)
@@ -151,6 +151,10 @@ idval:
    }
  ;
 
+conf: hostname_override ;
+
+hostname_override: HOSTNAME text ';' { new_config->hostname = $2; } ;
+
 conf: gr_opts ;
 
 gr_opts: GRACEFUL RESTART WAIT expr ';' { new_config->gr_wait = $4; } ;
diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index 302d026c..c54afe06 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -103,6 +103,7 @@
  * RFC 8654 - Extended Message Support for BGP
  * draft-ietf-idr-ext-opt-param-07
  * draft-uttaro-idr-bgp-persistence-04
+ * draft-walton-bgp-hostname-capability-02
  */
 
 #undef LOCAL_DEBUG
@@ -2415,6 +2416,9 @@ bgp_show_capabilities(struct bgp_proto *p UNUSED, struct bgp_caps *caps)
     bgp_show_afis(-1006, "        AF supported:", afl1, afn1);
     bgp_show_afis(-1006, "        AF preserved:", afl2, afn2);
   }
+
+  if (caps->hostname)
+    cli_msg(-1006, "      Hostname: %s", caps->hostname);
 }
 
 static void
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index dd7dc28f..cca4b448 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -98,6 +98,7 @@ struct bgp_config {
   int enable_refresh;			/* Enable local support for route refresh [RFC 2918] */
   int enable_as4;			/* Enable local support for 4B AS numbers [RFC 6793] */
   int enable_extended_messages;		/* Enable local support for extended messages [draft] */
+  int enable_hostname;			/* Enable local support for hostname [draft] */
   u32 rr_cluster_id;			/* Route reflector cluster ID, if different from local ID */
   int rr_client;			/* Whether neighbor is RR client of me */
   int rs_client;			/* Whether neighbor is RS client of me */
@@ -228,6 +229,8 @@ struct bgp_caps {
   u8 any_ext_next_hop;			/* Bitwise OR of per-AF ext_next_hop */
   u8 any_add_path;			/* Bitwise OR of per-AF add_path */
 
+  const char *hostname;			/* Hostname, RFC draft */
+
   u16 af_count;				/* Number of af_data items */
   u16 length;				/* Length of capabilities in OPEN msg */
 
diff --git a/proto/bgp/config.Y b/proto/bgp/config.Y
index 18c3560d..2dfbdca9 100644
--- a/proto/bgp/config.Y
+++ b/proto/bgp/config.Y
@@ -62,6 +62,7 @@ bgp_proto_start: proto_start BGP {
      BGP_CFG->error_delay_time_max = 300;
      BGP_CFG->enable_refresh = 1;
      BGP_CFG->enable_as4 = 1;
+     BGP_CFG->enable_hostname = 0;
      BGP_CFG->capabilities = 2;
      BGP_CFG->interpret_communities = 1;
      BGP_CFG->allow_as_sets = 1;
@@ -173,6 +174,7 @@ bgp_proto:
  | bgp_proto ENABLE ROUTE REFRESH bool ';' { BGP_CFG->enable_refresh = $5; }
  | bgp_proto ENABLE AS4 bool ';' { BGP_CFG->enable_as4 = $4; }
  | bgp_proto ENABLE EXTENDED MESSAGES bool ';' { BGP_CFG->enable_extended_messages = $5; }
+ | bgp_proto ADVERTISE HOSTNAME bool ';' { BGP_CFG->enable_hostname = $4; }
  | bgp_proto CAPABILITIES bool ';' { BGP_CFG->capabilities = $3; }
  | bgp_proto PASSWORD text ';' { BGP_CFG->password = $3; }
  | bgp_proto SETKEY bool ';' { BGP_CFG->setkey = $3; }
diff --git a/proto/bgp/packets.c b/proto/bgp/packets.c
index 78fdd1e0..b16ee242 100644
--- a/proto/bgp/packets.c
+++ b/proto/bgp/packets.c
@@ -252,6 +252,14 @@ bgp_prepare_capabilities(struct bgp_conn *conn)
   if (p->cf->llgr_mode)
     caps->llgr_aware = 1;
 
+  if (p->cf->enable_hostname && config->hostname)
+  {
+    size_t length = strlen(config->hostname);
+    char *hostname = mb_allocz(p->p.pool, length+1);
+    memcpy(hostname, config->hostname, length+1);
+    caps->hostname = hostname;
+  }
+
   /* Allocate and fill per-AF fields */
   WALK_LIST(c, p->p.channels)
   {
@@ -412,6 +420,24 @@ bgp_write_capabilities(struct bgp_conn *conn, byte *buf)
     data[-1] = buf - data;
   }
 
+  if (caps->hostname)
+  {
+    *buf++ = 73;                /* Capability 73: Hostname */
+    *buf++ = 0;			/* Capability data length */
+    data = buf;
+
+    /* Hostname */
+    size_t length = strlen(caps->hostname);
+    *buf++ = length;
+    memcpy(buf, caps->hostname, length);
+    buf += length;
+
+    /* Domain, not implemented */
+    *buf++ = 0;
+
+    data[-1] = buf - data;
+  }
+
   caps->length = buf - buf_head;
 
   return buf;
@@ -573,6 +599,21 @@ bgp_read_capabilities(struct bgp_conn *conn, byte *pos, int len)
       }
       break;
 
+    case 73: /* Hostname, RFC draft */
+      if ((cl < 2) || (cl < 2 + pos[2]))
+        goto err;
+
+      int length = pos[2];
+      char *hostname = mb_allocz(p->p.pool, length+1);
+      memcpy(hostname, pos + 3, length);
+      hostname[length] = 0;
+
+      for (i = 0; i < length; i++)
+        if (hostname[i] < ' ')
+          hostname[i] = ' ';
+
+      caps->hostname = hostname;
+
       /* We can safely ignore all other capabilities */
     }
 
diff --git a/sysdep/unix/main.c b/sysdep/unix/main.c
index 2c7e3cef..67e76655 100644
--- a/sysdep/unix/main.c
+++ b/sysdep/unix/main.c
@@ -20,6 +20,7 @@
 #include <pwd.h>
 #include <grp.h>
 #include <sys/stat.h>
+#include <sys/utsname.h>
 #include <libgen.h>
 
 #include "nest/bird.h"
@@ -88,6 +89,21 @@ drop_gid(gid_t gid)
     die("setgroups: %m");
 }
 
+/*
+ *	Hostname
+ */
+
+char *
+get_hostname(linpool *lp)
+{
+  struct utsname uts = {};
+
+  if (uname(&uts) < 0)
+      return NULL;
+
+  return lp_strdup(lp, uts.nodename);
+}
+
 /*
  *	Reading the Configuration
  */
diff --git a/sysdep/unix/unix.h b/sysdep/unix/unix.h
index 0f2973f0..ad85d1ea 100644
--- a/sysdep/unix/unix.h
+++ b/sysdep/unix/unix.h
@@ -24,6 +24,7 @@ extern int parse_and_exit;
 void async_config(void);
 void async_dump(void);
 void async_shutdown(void);
+char *get_hostname(linpool *lp);
 void cmd_check_config(const char *name);
 void cmd_reconfig(const char *name, int type, uint timeout);
 void cmd_reconfig_confirm(void);