From: Maria Matejka <mq@ucw.cz>
Date: Mon, 9 Sep 2024 12:14:49 +0000 (+0200)
Subject: Flock: Hypervisor control socket CBOR push parser
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9babba1c0f718a60e10c82208319280433e7eb94;p=thirdparty%2Fbird.git

Flock: Hypervisor control socket CBOR push parser

It reads some data, the actions are not implemented yet.
---

diff --git a/flock/Makefile b/flock/Makefile
index debbd66cb..c873e169e 100644
--- a/flock/Makefile
+++ b/flock/Makefile
@@ -1,4 +1,4 @@
-src := flock.c hypervisor.c
+src := ctl.c flock.c hypervisor.c
 obj := $(src-o-files)
 
 flock=$(exedir)/flock-sim
diff --git a/flock/ctl.c b/flock/ctl.c
new file mode 100644
index 000000000..d94bae755
--- /dev/null
+++ b/flock/ctl.c
@@ -0,0 +1,300 @@
+#include "lib/birdlib.h"
+#include "lib/string.h"
+
+#include "flock/flock.h"
+
+#include <stdlib.h>
+
+/*
+ * Hand-written parser for a very simple CBOR protocol:
+ *
+ * - on toplevel always mapping of one element
+ * - key of the element may be:
+ *   - 0 with NULL (7-22) = shutdown the hypervisor
+ *   - 1 with NULL = open a telnet listener
+ *   - 2 with NULL = close the telnet listener (if not used)
+ *   - 3 with array of strings = run the given command inside the hypervisor
+ */
+
+struct cbor_parser_context {
+  linpool *lp;
+
+  PACKED enum {
+    CPE_TYPE = 0,
+    CPE_READ_INT,
+    CPE_COMPLETE_INT,
+    CPE_READ_BYTE,
+  } partial_state, partial_next;
+
+  byte type;
+  u64 value;
+  u64 partial_countdown;
+
+  u64 bytes_consumed;
+
+  byte *target_buf;
+  uint target_len;
+
+  u64 major_state;
+
+  const char *error;
+
+#define LOCAL_STACK_MAX_DEPTH 3
+  u64 stack_countdown[LOCAL_STACK_MAX_DEPTH];
+  uint stack_pos;
+};
+
+#define CBOR_PARSER_ERROR(...)	do {		\
+  ctx->error = lp_sprintf(ctx->lp, __VA_ARGS__);\
+  return -(ctx->bytes_consumed + pos + 1);	\
+} while (0)
+
+#define CBOR_PARSER_READ_INT(next)  do {		\
+  ctx->partial_state = CPE_READ_INT;			\
+  ctx->partial_countdown = (1 << (ctx->value - 24));	\
+  ctx->value = 0;					\
+  ctx->partial_next = next;				\
+} while (0)
+
+struct cbor_parser_context *
+hcs_parser_init(pool *p)
+{
+  linpool *lp = lp_new(p);
+  struct cbor_parser_context *ctx = lp_allocz(lp, sizeof *ctx);
+
+  ctx->lp = lp;
+
+  ctx->type = 0xff;
+  ctx->stack_countdown[0] = 1;
+
+  return ctx;
+}
+
+s64
+hcs_parse(struct cbor_parser_context *ctx, const byte *buf, s64 size)
+{
+  ASSERT_DIE(size > 0);
+
+  for (int pos = 0; pos < size; pos++)
+  {
+    const byte bp = buf[pos];
+    bool value_is_special = 0;
+    bool exit_stack = false;
+
+    switch (ctx->partial_state)
+    {
+      case CPE_TYPE:
+	/* Split the byte to type and value */
+	ctx->type = bp >> 5;
+	ctx->value = bp & 0x1f;
+
+	if (ctx->type == 7)
+	{
+	  if (ctx->value < 20)
+	    CBOR_PARSER_ERROR("Unknown simple value %u", ctx->value);
+	  else if (ctx->value < 24)
+	    ; /* false, true, null, undefined */
+	  else if (ctx->value < 28)
+	  {
+	    /* Need more data */
+	    CBOR_PARSER_READ_INT(CPE_COMPLETE_INT);
+	    break;
+	  }
+	  else if (ctx->value == 31)
+	    ; /* break-stop */
+	  else
+	    CBOR_PARSER_ERROR("Unknown simple value %u", ctx->value);
+	}
+	else
+	{
+	  if (ctx->value < 24)
+	    ; /* Immediate value, fall through */
+	  else if (ctx->value < 28)
+	  {
+	    /* Need more data */
+	    CBOR_PARSER_READ_INT(CPE_COMPLETE_INT);
+	    break;
+	  }
+	  else if ((ctx->value == 31) && (ctx->type >= 2) && (ctx->type <= 5))
+	    /* Indefinite length, fall through */
+	    value_is_special = 1;
+	  else
+	    CBOR_PARSER_ERROR("Garbled additional value %u for type %u", ctx->value, ctx->type);
+	}
+	/* fall through */
+
+      case CPE_READ_INT:
+	if (ctx->partial_state == CPE_READ_INT)
+	{
+	  /* Reading a network order integer */
+	  ctx->value <<= 8;
+	  ctx->value |= bp;
+	  if (--ctx->partial_countdown)
+	    break;
+	}
+	/* fall through */
+
+      case CPE_COMPLETE_INT:
+	/* TODO: exception for 7-31 end of long thing */
+
+	/* Check type acceptance */
+	switch (ctx->major_state)
+	{
+	  case 0: /* toplevel */
+	    if (ctx->type != 5)
+	      CBOR_PARSER_ERROR("Expected mapping, got %u", ctx->type);
+
+	    if (ctx->value != 1)
+	      CBOR_PARSER_ERROR("Expected mapping of length 1, got %u", ctx->value);
+
+	    ctx->major_state = 1;
+	    break;
+
+	  case 1: /* inside toplevel mapping */
+	    if (ctx->type != 0)
+	      CBOR_PARSER_ERROR("Expected integer, got %u", ctx->type);
+	    
+	    if (ctx->value >= 4)
+	      CBOR_PARSER_ERROR("Command key too high, got %lu", ctx->value);
+
+	    ctx->major_state = ctx->value + 2;
+	    break;
+
+	  case 2: /* shutdown command: expected null */
+	    if ((ctx->type != 7) || (ctx->value != 22))
+	      CBOR_PARSER_ERROR("Expected null, got %u-%u", ctx->type, ctx->value);
+
+	    log(L_INFO "Requested shutdown");
+	    ctx->major_state = 1;
+	    break;
+
+	  case 3: /* telnet listener open */
+	    if ((ctx->type != 7) || (ctx->value != 22))
+	      CBOR_PARSER_ERROR("Expected null, got %u-%u", ctx->type, ctx->value);
+
+	    log(L_INFO "Requested telnet open");
+	    ctx->major_state = 1;
+	    break;
+
+	  case 4: /* telnet listener close */
+	    if ((ctx->type != 7) || (ctx->value != 22))
+	      CBOR_PARSER_ERROR("Expected null, got %u-%u", ctx->type, ctx->value);
+
+	    log(L_INFO "Requested telnet close");
+	    ctx->major_state = 1;
+	    break;
+
+	  case 5: /* process spawner */
+	    CBOR_PARSER_ERROR("NOT IMPLEMENTED YET");
+	    break;
+
+	  default:
+	    bug("invalid parser state");
+	}
+
+	/* Some types are completely parsed, some not yet */
+	switch (ctx->type)
+	{
+	  case 0:
+	  case 1:
+	  case 7:
+	    exit_stack = !--ctx->stack_countdown[ctx->stack_pos];
+	    ctx->partial_state = CPE_TYPE;
+	    break;
+
+	  case 2:
+	  case 3:
+	    ctx->partial_state = CPE_READ_BYTE;
+	    ctx->partial_countdown = ctx->value;
+	    ctx->target_buf = ctx->target_buf ?: lp_allocu(
+		ctx->lp, ctx->target_len = (ctx->target_len ?: ctx->value));
+	    break;
+
+	  case 4:
+	  case 5:
+	    if (++ctx->stack_pos >= LOCAL_STACK_MAX_DEPTH)
+	      CBOR_PARSER_ERROR("Stack too deep");
+
+	    /* set array/map size;
+	     * once for arrays, twice for maps;
+	     * ~0 for indefinite */
+	    ctx->stack_countdown[ctx->stack_pos] = value_is_special ? ~0ULL :
+	      (ctx->value * (ctx->type - 3));
+	    ctx->partial_state = CPE_TYPE;
+	    break;
+	}
+
+	break;
+
+      case CPE_READ_BYTE:
+	*ctx->target_buf = bp;
+	ctx->target_buf++;
+	if (--ctx->target_len)
+	  break;
+
+	/* Read completely! */
+	switch (ctx->major_state)
+	{
+	  case 5:
+	    /* Actually not this one */
+	    CBOR_PARSER_ERROR("NOT IMPLEMENTED YET");
+
+	  default:
+	    bug("Unexpected state to end a (byte)string in");
+	  /* Code to run at the end of a (byte)string */
+	}
+
+	exit_stack = !--ctx->stack_countdown[ctx->stack_pos];
+    }
+
+    /* End of array or map */
+    while (exit_stack)
+    {
+      switch (ctx->major_state)
+      {
+	/* Code to run at the end of the mapping */
+	case 0: /* toplevel item ended */
+	  ctx->major_state = ~0ULL;
+	  return pos + 1;
+
+	case 1:
+	  ctx->major_state = 0;
+	  break;
+
+	case 5:
+	  /* Finalize the command to exec in hypervisor */
+	  CBOR_PARSER_ERROR("NOT IMPLEMENTED YET");
+	  ctx->major_state = 1;
+	  break;
+
+	default:
+	  bug("Unexpected state to end a mapping in");
+      }
+
+      /* Check exit from the next item */
+      ASSERT_DIE(ctx->stack_pos);
+      exit_stack = !--ctx->stack_countdown[--ctx->stack_pos];
+    }
+  }
+
+  ctx->bytes_consumed += size;
+  return size;
+}
+
+bool
+hcs_complete(struct cbor_parser_context *ctx)
+{
+  return ctx->major_state == ~0ULL;
+}
+
+const char *
+hcs_error(struct cbor_parser_context *ctx)
+{
+  return ctx->error;
+}
+
+void
+hcs_parser_cleanup(struct cbor_parser_context *ctx)
+{
+  rfree(ctx->lp);
+}
diff --git a/flock/flock.h b/flock/flock.h
index 988e4fa81..4a7956fa5 100644
--- a/flock/flock.h
+++ b/flock/flock.h
@@ -3,6 +3,7 @@
 #ifndef INCLUDE_FLOCK_H
 #define INCLUDE_FLOCK_H
 #include "lib/birdlib.h"
+#include "lib/resource.h"
 
 void hypervisor_exposed_fork(void);
 void hypervisor_control_socket(void);
@@ -15,4 +16,10 @@ struct flock_config {
 
 extern struct flock_config flock_config;
 
+struct cbor_parser_context *hcs_parser_init(pool *p);
+s64 hcs_parse(struct cbor_parser_context *ctx, const byte *buf, s64 size);
+void hcs_parser_cleanup(struct cbor_parser_context *ctx);
+const char *hcs_error(struct cbor_parser_context *ctx);
+bool hcs_complete(struct cbor_parser_context *ctx);
+
 #endif
diff --git a/flock/hypervisor.c b/flock/hypervisor.c
index 0f62c52be..2b52396db 100644
--- a/flock/hypervisor.c
+++ b/flock/hypervisor.c
@@ -14,11 +14,53 @@
 
 pool *hypervisor_control_socket_pool;
 
+static int
+hcs_rx(sock *s, uint size)
+{
+  s64 sz = hcs_parse(s->data, s->rbuf, size);
+  if (sz < 0)
+  {
+    log(L_INFO "CLI parser error at position %ld: %s", -sz-1, hcs_error(s->data));
+    sk_close(s);
+    return 0; /* Must return 0 when closed */
+  }
+
+  if (!hcs_complete(s->data))
+  {
+    ASSERT_DIE(sz == size);
+    return 1;
+  }
+
+  log(L_INFO "Parsed command.");
+
+  /* TODO do something more */
+
+  hcs_parser_cleanup(s->data);
+  s->data = hcs_parser_init(s->pool);
+
+  if (sz == size)
+    return 1;
+
+  memmove(s->rbuf, s->rbuf + sz, size - sz);
+  return hcs_rx(s, size - sz);
+}
+
+static void
+hcs_err(sock *s, int err)
+{
+  log(L_INFO "CLI dropped: %s", strerror(err));
+  hcs_parser_cleanup(s->data);
+  sk_close(s);
+}
+
 static int
 hcs_connect(sock *s, uint size UNUSED)
 {
   log(L_INFO "CLI connected: %p", s);
-  sk_close(s);
+
+  s->rx_hook = hcs_rx;
+  s->err_hook = hcs_err;
+  s->data = hcs_parser_init(s->pool);
   return 1;
 }