[iptables PATCH 1/3] nft: Reject standard targets as chain names when restoring

[Phil Sutter <phil@nwl.cc>]

Reuse parse_chain() called from do_parse() for '-N' and rename it for a
better description of what it does.

Note that by itself, this patch will likely kill iptables-restore
performance for big rulesets due to the extra extension lookup for chain
lines. A following patch announcing those chains to libxtables will
alleviate that.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 iptables/xshared.c         | 4 ++--
 iptables/xshared.h         | 2 +-
 iptables/xtables-restore.c | 5 +----
 3 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/iptables/xshared.c b/iptables/xshared.c
index 43321d3b5358c..00828c8ae87d9 100644
--- a/iptables/xshared.c
+++ b/iptables/xshared.c
@@ -1031,7 +1031,7 @@ set_option(unsigned int *options, unsigned int option, u_int16_t *invflg,
 	}
 }
 
-void parse_chain(const char *chainname)
+void assert_valid_chain_name(const char *chainname)
 {
 	const char *ptr;
 
@@ -1412,7 +1412,7 @@ void do_parse(int argc, char *argv[],
 			break;
 
 		case 'N':
-			parse_chain(optarg);
+			assert_valid_chain_name(optarg);
 			add_command(&p->command, CMD_NEW_CHAIN, CMD_NONE,
 				    invert);
 			p->chain = optarg;
diff --git a/iptables/xshared.h b/iptables/xshared.h
index 0de0e12e5a922..ca761ee7246ad 100644
--- a/iptables/xshared.h
+++ b/iptables/xshared.h
@@ -244,7 +244,7 @@ char cmd2char(int option);
 void add_command(unsigned int *cmd, const int newcmd,
 		 const int othercmds, int invert);
 int parse_rulenumber(const char *rule);
-void parse_chain(const char *chainname);
+void assert_valid_chain_name(const char *chainname);
 
 void generic_opt_check(int command, int options);
 char opt2char(int option);
diff --git a/iptables/xtables-restore.c b/iptables/xtables-restore.c
index 81b25a43c9a04..c94770a0175eb 100644
--- a/iptables/xtables-restore.c
+++ b/iptables/xtables-restore.c
@@ -155,10 +155,7 @@ static void xtables_restore_parse_line(struct nft_handle *h,
 				   "%s: line %u chain name invalid\n",
 				   xt_params->program_name, line);
 
-		if (strlen(chain) >= XT_EXTENSION_MAXNAMELEN)
-			xtables_error(PARAMETER_PROBLEM,
-				   "Invalid chain name `%s' (%u chars max)",
-				   chain, XT_EXTENSION_MAXNAMELEN - 1);
+		assert_valid_chain_name(chain);
 
 		policy = strtok(NULL, " \t\n");
 		DEBUGP("line %u, policy '%s'\n", line, policy);
-- 
2.34.1