Decode BGP Shutdown Communication messages (RFC 8203)

[Job Snijders]

Spin #2

---
 proto/bgp/bgp.c     | 12 +++++++++
 proto/bgp/bgp.h     |  2 ++
 proto/bgp/packets.c | 73 ++++++++++++++++++++++++++++++++++-------------------
 3 files changed, 61 insertions(+), 26 deletions(-)

diff --git a/proto/bgp/bgp.c b/proto/bgp/bgp.c
index f706e76..2a89c00 100644
--- a/proto/bgp/bgp.c
+++ b/proto/bgp/bgp.c
@@ -1487,6 +1487,15 @@ bgp_last_errmsg(struct bgp_proto *p)
 }
 
 static const char *
+bgp_last_shutmsg(struct bgp_proto *p)
+{
+    if (p->last_received_shutmsg)
+      return(p->last_received_shutmsg);
+    else
+      return(NULL);
+}
+
+static const char *
 bgp_state_dsc(struct bgp_proto *p)
 {
   if (p->p.proto_state == PS_DOWN)
@@ -1580,7 +1589,10 @@ bgp_show_proto_info(struct proto *P)
     {
       const char *err1 = bgp_err_classes[p->last_error_class];
       const char *err2 = bgp_last_errmsg(p);
+      const char *msg  = bgp_last_shutmsg(p);
       cli_msg(-1006, "    Last error:       %s%s", err1, err2);
+      if (msg)
+        cli_msg(-1006, "    Message:          \"%s\"", msg);
     }
 }
 
diff --git a/proto/bgp/bgp.h b/proto/bgp/bgp.h
index e47a0eb..d958716 100644
--- a/proto/bgp/bgp.h
+++ b/proto/bgp/bgp.h
@@ -157,6 +157,8 @@ struct bgp_proto {
   u8 last_error_class; 			/* Error class of last error */
   u32 last_error_code;			/* Error code of last error. BGP protocol errors
 					   are encoded as (bgp_err_code << 16 | bgp_err_subcode) */
+  byte last_received_shutmsg[129];		/* RFC 8203 */
+
 #ifdef IPV6
   byte *mp_reach_start, *mp_unreach_start; /* Multiprotocol BGP attribute notes */
   unsigned mp_reach_len, mp_unreach_len;
diff --git a/proto/bgp/packets.c b/proto/bgp/packets.c
index ab87bdc..a44f264 100644
--- a/proto/bgp/packets.c
+++ b/proto/bgp/packets.c
@@ -1460,9 +1460,9 @@ static struct {
   { 5, 3, "Unexpected message in Established state" },
   { 6, 0, "Cease" }, /* Subcodes are according to [RFC4486] */
   { 6, 1, "Maximum number of prefixes reached" },
-  { 6, 2, "Administrative shutdown" },
+  { 6, 2, "Administrative shutdown" }, /* RFC 8203 can follow */
   { 6, 3, "Peer de-configured" },
-  { 6, 4, "Administrative reset" },
+  { 6, 4, "Administrative reset" }, /* RFC 8203 can follow */
   { 6, 5, "Connection rejected" },
   { 6, 6, "Other configuration change" },
   { 6, 7, "Connection collision resolution" },
@@ -1497,35 +1497,56 @@ bgp_error_dsc(unsigned code, unsigned subcode)
 void
 bgp_log_error(struct bgp_proto *p, u8 class, char *msg, unsigned code, unsigned subcode, byte *data, unsigned len)
 {
-  const byte *name;
-  byte *t, argbuf[36];
-  unsigned i;
+    const byte *name;
+    byte *t, argbuf[256];
+    unsigned i;
+    unsigned shutdown_comm_length;
 
-  /* Don't report Cease messages generated by myself */
-  if (code == 6 && class == BE_BGP_TX)
-    return;
+    /* Don't report Cease messages generated by myself */
+    if (code == 6 && class == BE_BGP_TX)
+        return;
+
+    name = bgp_error_dsc(code, subcode);
+    t = argbuf;
+    memset(p->last_received_shutmsg, 0, 128 + 1); // clear old RFC 8203 messages
 
-  name = bgp_error_dsc(code, subcode);
-  t = argbuf;
-  if (len)
+    if (len)
     {
-      *t++ = ':';
-      *t++ = ' ';
+        *t++ = ':';
+        *t++ = ' ';
 
-      if ((code == 2) && (subcode == 2) && ((len == 2) || (len == 4)))
-	{
-	  /* Bad peer AS - we would like to print the AS */
-	  t += bsprintf(t, "%d", (len == 2) ? get_u16(data) : get_u32(data));
-	  goto done;
-	}
-      if (len > 16)
-	len = 16;
-      for (i=0; i<len; i++)
-	t += bsprintf(t, "%02x", data[i]);
+        if ((code == 2) && (subcode == 2) && ((len == 2) || (len == 4)))
+        {
+            /* Bad peer AS - we would like to print the AS */
+            t += bsprintf(t, "%d", (len == 2) ? get_u16(data) : get_u32(data));
+            goto done;
+        }
+        /* RFC 8203 */
+        if ((code == 6) && ((subcode == 2 || subcode == 4)) && (len <= 129))
+        {
+            shutdown_comm_length = data[0];
+            if ((shutdown_comm_length <= 128) && (len == shutdown_comm_length + 1))
+            {
+                t += bsprintf(t, "\"");
+                for (i=1; i<len; i++)
+                    t += bsprintf(t, "%c", data[i]);
+                t += bsprintf(t, "\"");
+                memcpy(p->last_received_shutmsg, data + 1, shutdown_comm_length);
+                goto done;
+            }
+        }
+        else
+        {
+            if (len > 16)
+                len = 16;
+            for (i=0; i<len; i++)
+                t += bsprintf(t, "%02x", data[i]);
+        }
     }
- done:
-  *t = 0;
-  log(L_REMOTE "%s: %s: %s%s", p->p.name, msg, name, argbuf);
+
+  done:
+    *t = 0;
+    log(L_REMOTE "%s: %s: %s%s", p->p.name, msg, name, argbuf);
 }
 
 static void