Add `missing` and `or-flush` options to "ipfw table <NAME> create"

command to simplify firewall reloading.

The `missing` option suppresses EEXIST error code, but does check that
existing table has the same parameters as new one. The `or-flush` option
implies `missing` option and additionally does flush for table if it
is already exist.

Submitted by:	lev
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D18339

3 files changed, 45 insertions, 7 deletions

diff --git a/sbin/ipfw/ipfw.8 b/sbin/ipfw/ipfw.8
index cf0c3affe029..fcba4a4b03f2 100644
--- a/sbin/ipfw/ipfw.8
+++ b/sbin/ipfw/ipfw.8
@@ -1,7 +1,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd April 21, 2019
+.Dd May 24, 2019
 .Dt IPFW 8
 .Os
 .Sh NAME
@@ -2138,7 +2138,7 @@ The following creation options are supported:
 .Bl -tag -width indent
 .It Ar create-options : Ar create-option | create-options
 .It Ar create-option : Cm type Ar table-type | Cm valtype Ar value-mask | Cm algo Ar algo-desc |
-.Cm limit Ar number | Cm locked
+.Cm limit Ar number | Cm locked | Cm missing | Cm or-flush
 .It Cm type
 Table key type.
 .It Cm valtype
@@ -2149,6 +2149,13 @@ Table algorithm to use (see below).
 Maximum number of items that may be inserted into table.
 .It Cm locked
 Restrict any table modifications.
+.It Cm missing
+Do not fail if table already exists and has exactly same options as new one.
+.It Cm or-flush
+Flush existing table with same name instead of returning error.
+Implies
+.Cm missing
+so existing table must be compatible with new one.
 .El
 .Pp
 Some of these options may be modified later via
diff --git a/sbin/ipfw/ipfw2.h b/sbin/ipfw/ipfw2.h
index 2b562734d15f..659285366c2c 100644
--- a/sbin/ipfw/ipfw2.h
+++ b/sbin/ipfw/ipfw2.h
@@ -264,6 +264,9 @@ enum tokens {
 	TOK_UNLOCK,
 	TOK_VLIST,
 	TOK_OLIST,
+	TOK_MISSING,
+	TOK_ORFLUSH,
+	TOK_OPTIONAL,
 
 	/* NAT64 tokens */
 	TOK_NAT64STL,
diff --git a/sbin/ipfw/tables.c b/sbin/ipfw/tables.c
index 3fa806348a27..4be24210d4f0 100644
--- a/sbin/ipfw/tables.c
+++ b/sbin/ipfw/tables.c
@@ -327,6 +327,8 @@ static struct _s_x tablenewcmds[] = {
       { "algo",		TOK_ALGO },
       { "limit",	TOK_LIMIT },
       { "locked",	TOK_LOCK },
+      { "missing",	TOK_MISSING },
+      { "or-flush",	TOK_ORFLUSH },
       { NULL, 0 }
 };
 
@@ -389,19 +391,19 @@ table_print_type(char *tbuf, size_t size, uint8_t type, uint8_t tflags)
  * Creates new table
  *
  * ipfw table NAME create [ type { addr | iface | number | flow } ]
- *     [ algo algoname ]
+ *     [ algo algoname ] [missing] [or-flush]
  */
 static void
 table_create(ipfw_obj_header *oh, int ac, char *av[])
 {
-	ipfw_xtable_info xi;
-	int error, tcmd, val;
+	ipfw_xtable_info xi, xie;
+	int error, missing, orflush, tcmd, val;
 	uint32_t fset, fclear;
 	char *e, *p;
 	char tbuf[128];
 
+	missing = orflush = 0;
 	memset(&xi, 0, sizeof(xi));
-
 	while (ac > 0) {
 		tcmd = get_token(tablenewcmds, *av, "option");
 		ac--; av++;
@@ -457,6 +459,12 @@ table_create(ipfw_obj_header *oh, int ac, char *av[])
 		case TOK_LOCK:
 			xi.flags |= IPFW_TGFLAGS_LOCKED;
 			break;
+		case TOK_ORFLUSH:
+			orflush = 1;
+			/* FALLTHROUGH */
+		case TOK_MISSING:
+			missing = 1;
+			break;
 		}
 	}
 
@@ -466,8 +474,28 @@ table_create(ipfw_obj_header *oh, int ac, char *av[])
 	if (xi.vmask == 0)
 		xi.vmask = IPFW_VTYPE_LEGACY;
 
-	if ((error = table_do_create(oh, &xi)) != 0)
+	error = table_do_create(oh, &xi);
+
+	if (error == 0)
+		return;
+
+	if (errno != EEXIST || missing == 0)
 		err(EX_OSERR, "Table creation failed");
+
+	/* Check that existing table is the same we are trying to create */
+	if (table_get_info(oh, &xie) != 0)
+		err(EX_OSERR, "Existing table check failed");
+
+	if (xi.limit != xie.limit || xi.type != xie.type ||
+	    xi.tflags != xie.tflags || xi.vmask != xie.vmask || (
+	    xi.algoname[0] != '\0' && strcmp(xi.algoname,
+	    xie.algoname) != 0) || xi.flags != xie.flags)
+		errx(EX_DATAERR, "The existing table is not compatible "
+		    "with one you are creating.");
+
+	/* Flush existing table if instructed to do so */
+	if (orflush != 0 && table_flush(oh) != 0)
+		err(EX_OSERR, "Table flush on creation failed");
 }
 
 /*