[PATCH 1/3] extensions: libtxt_NFLOG: use nft built-in logging instead of xt_NFLOG

[Kyle Bowman <kbowman@cloudflare.com>]

Replaces the use of xt_NFLOG with the nft built-in log statement.

This additionally adds support for using longer log prefixes of 128
characters in size. Until now NFLOG has truncated the log-prefix to the
64-character limit supported by iptables-legacy. We now use the struct
xtables_target's udata member to store the longer 128-character prefix
supported by iptables-nft.

Signed-off-by: Kyle Bowman <kbowman@cloudflare.com>
Signed-off-by: Alex Forster <aforster@cloudflare.com>
Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
---
 extensions/libxt_NFLOG.c |  6 ++++++
 iptables/nft.c           | 28 ++++++++++++++++++++++++++++
 iptables/nft.h           |  1 +
 3 files changed, 35 insertions(+)

diff --git a/extensions/libxt_NFLOG.c b/extensions/libxt_NFLOG.c
index 02a1b4aa..2b78e278 100644
--- a/extensions/libxt_NFLOG.c
+++ b/extensions/libxt_NFLOG.c
@@ -5,6 +5,7 @@
 #include <getopt.h>
 #include <xtables.h>
 
+#include <linux/netfilter/nf_log.h>
 #include <linux/netfilter/x_tables.h>
 #include <linux/netfilter/xt_NFLOG.h>
 
@@ -53,12 +54,16 @@ static void NFLOG_init(struct xt_entry_target *t)
 
 static void NFLOG_parse(struct xt_option_call *cb)
 {
+	char *nf_log_prefix = cb->udata;
+
 	xtables_option_parse(cb);
 	switch (cb->entry->id) {
 	case O_PREFIX:
 		if (strchr(cb->arg, '\n') != NULL)
 			xtables_error(PARAMETER_PROBLEM,
 				   "Newlines not allowed in --log-prefix");
+
+		snprintf(nf_log_prefix, NF_LOG_PREFIXLEN, "%s", cb->arg);
 		break;
 	}
 }
@@ -149,6 +154,7 @@ static struct xtables_target nflog_target = {
 	.save		= NFLOG_save,
 	.x6_options	= NFLOG_opts,
 	.xlate		= NFLOG_xlate,
+	.udata_size	= NF_LOG_PREFIXLEN
 };
 
 void _init(void)
diff --git a/iptables/nft.c b/iptables/nft.c
index 795dff86..aebbf674 100644
--- a/iptables/nft.c
+++ b/iptables/nft.c
@@ -39,6 +39,7 @@
 #include <linux/netfilter/nf_tables_compat.h>
 
 #include <linux/netfilter/xt_limit.h>
+#include <linux/netfilter/xt_NFLOG.h>
 
 #include <libmnl/libmnl.h>
 #include <libnftnl/gen.h>
@@ -1340,6 +1341,8 @@ int add_action(struct nftnl_rule *r, struct iptables_command_state *cs,
 		       ret = add_verdict(r, NF_DROP);
 	       else if (strcmp(cs->jumpto, XTC_LABEL_RETURN) == 0)
 		       ret = add_verdict(r, NFT_RETURN);
+	       else if (strcmp(cs->jumpto, "NFLOG") == 0)
+		       ret = add_log(r, cs);
 	       else
 		       ret = add_target(r, cs->target->t);
        } else if (strlen(cs->jumpto) > 0) {
@@ -1352,6 +1355,31 @@ int add_action(struct nftnl_rule *r, struct iptables_command_state *cs,
        return ret;
 }
 
+int add_log(struct nftnl_rule *r, struct iptables_command_state *cs)
+{
+	struct nftnl_expr *expr;
+	struct xt_nflog_info *info = (struct xt_nflog_info *)cs->target->t->data;
+
+	expr = nftnl_expr_alloc("log");
+	if (!expr)
+		return -ENOMEM;
+
+	if (info->prefix[0] != '\0') {
+		nftnl_expr_set_str(expr, NFTNL_EXPR_LOG_PREFIX, cs->target->udata);
+	}
+
+	nftnl_expr_set_u16(expr, NFTNL_EXPR_LOG_GROUP, info->group);
+	if (info->flags & XT_NFLOG_F_COPY_LEN)
+		nftnl_expr_set_u32(expr, NFTNL_EXPR_LOG_SNAPLEN,
+				info->len);
+	if (info->threshold)
+		nftnl_expr_set_u16(expr, NFTNL_EXPR_LOG_QTHRESHOLD,
+				info->threshold);
+
+	nftnl_rule_add_expr(r, expr);
+	return 0;
+}
+
 static void nft_rule_print_debug(struct nftnl_rule *r, struct nlmsghdr *nlh)
 {
 #ifdef NLDEBUG
diff --git a/iptables/nft.h b/iptables/nft.h
index 4ac7e009..28dc81b7 100644
--- a/iptables/nft.h
+++ b/iptables/nft.h
@@ -193,6 +193,7 @@ int add_match(struct nft_handle *h, struct nftnl_rule *r, struct xt_entry_match
 int add_target(struct nftnl_rule *r, struct xt_entry_target *t);
 int add_jumpto(struct nftnl_rule *r, const char *name, int verdict);
 int add_action(struct nftnl_rule *r, struct iptables_command_state *cs, bool goto_set);
+int add_log(struct nftnl_rule *r, struct iptables_command_state *cs);
 char *get_comment(const void *data, uint32_t data_len);
 
 enum nft_rule_print {
-- 
2.20.1