libxtables: xt_xlate_add() to take care of spacing

Try to eliminate most of the whitespace issues by separating strings
from separate xt_xlate_add() calls by whitespace if needed.

Cover the common case of consecutive range, list or MAC/IP address
printing by inserting whitespace only if the string to be appended
starts with an alphanumeric character or a brace. The latter helps to
make spacing in anonymous sets consistent.

Provide *_nospc() variants which disable the auto-spacing for the
mandatory exception to the rule.

Make things round by dropping any trailing whitespace before returning
the buffer via xt_xlate_get().

Signed-off-by: Phil Sutter <phil@nwl.cc>

8 files changed, 66 insertions, 18 deletions

diff --git a/extensions/libxt_dccp.txlate b/extensions/libxt_dccp.txlate
index ea853f6a..be950bcb 100644
--- a/extensions/libxt_dccp.txlate
+++ b/extensions/libxt_dccp.txlate
@@ -14,7 +14,7 @@ iptables-translate -A INPUT -p dccp -m dccp --dccp-types INVALID
 nft add rule ip filter INPUT dccp type 10-15 counter
 
 iptables-translate -A INPUT -p dccp -m dccp --dport 100 --dccp-types REQUEST,RESPONSE,DATA,ACK,DATAACK,CLOSEREQ,CLOSE,SYNC,SYNCACK,INVALID
-nft add rule ip filter INPUT dccp dport 100 dccp type {request, response, data, ack, dataack, closereq, close, sync, syncack, 10-15} counter
+nft add rule ip filter INPUT dccp dport 100 dccp type { request, response, data, ack, dataack, closereq, close, sync, syncack, 10-15 } counter
 
 iptables-translate -A INPUT -p dccp -m dccp --sport 200 --dport 100
 nft add rule ip filter INPUT dccp sport 200 dccp dport 100 counter
diff --git a/extensions/libxt_hashlimit.c b/extensions/libxt_hashlimit.c
index 93ee1c32..24e784ab 100644
--- a/extensions/libxt_hashlimit.c
+++ b/extensions/libxt_hashlimit.c
@@ -1270,7 +1270,7 @@ static void hashlimit_print_subnet_xlate(struct xt_xlate *xl,
 			}
 		}
 
-		xt_xlate_add(xl, fmt, acm);
+		xt_xlate_add_nospc(xl, fmt, acm);
 		if (nblocks > 0)
 			xt_xlate_add(xl, "%c", sep);
 	}
diff --git a/extensions/libxt_hashlimit.txlate b/extensions/libxt_hashlimit.txlate
index 6c8d07f1..251a30d3 100644
--- a/extensions/libxt_hashlimit.txlate
+++ b/extensions/libxt_hashlimit.txlate
@@ -1,5 +1,5 @@
 iptables-translate -A OUTPUT -m tcp -p tcp --dport 443 -m hashlimit --hashlimit-above 20kb/s --hashlimit-burst 1mb --hashlimit-mode dstip --hashlimit-name https --hashlimit-dstmask 24 -m state --state NEW -j DROP
-nft add rule ip filter OUTPUT tcp dport 443 meter https { ip daddr and 255.255.255.0 timeout 60s limit rate over 20 kbytes/second burst 1 mbytes} ct state new  counter drop
+nft add rule ip filter OUTPUT tcp dport 443 meter https { ip daddr and 255.255.255.0 timeout 60s limit rate over 20 kbytes/second burst 1 mbytes } ct state new  counter drop
 
 iptables-translate -A OUTPUT -m tcp -p tcp --dport 443 -m hashlimit --hashlimit-upto 300 --hashlimit-burst 15 --hashlimit-mode srcip,dstip --hashlimit-name https --hashlimit-htable-expire 300000 -m state --state NEW -j DROP
-nft add rule ip filter OUTPUT tcp dport 443 meter https { ip daddr . ip saddr timeout 300s limit rate 300/second burst 15 packets} ct state new  counter drop
+nft add rule ip filter OUTPUT tcp dport 443 meter https { ip daddr . ip saddr timeout 300s limit rate 300/second burst 15 packets } ct state new  counter drop
diff --git a/extensions/libxt_multiport.txlate b/extensions/libxt_multiport.txlate
index bced1b84..bf015265 100644
--- a/extensions/libxt_multiport.txlate
+++ b/extensions/libxt_multiport.txlate
@@ -1,5 +1,5 @@
 iptables-translate -t filter -A INPUT -p tcp -m multiport --dports 80,81 -j ACCEPT
-nft add rule ip filter INPUT ip protocol tcp tcp dport { 80,81} counter accept
+nft add rule ip filter INPUT ip protocol tcp tcp dport { 80,81 } counter accept
 
 iptables-translate -t filter -A INPUT -p tcp -m multiport --dports 80:88 -j ACCEPT
 nft add rule ip filter INPUT ip protocol tcp tcp dport 80-88 counter accept
diff --git a/extensions/libxt_tcp.c b/extensions/libxt_tcp.c
index 043382d4..2ef84299 100644
--- a/extensions/libxt_tcp.c
+++ b/extensions/libxt_tcp.c
@@ -380,10 +380,9 @@ static void print_tcp_xlate(struct xt_xlate *xl, uint8_t flags)
 
 		for (i = 0; (flags & tcp_flag_names_xlate[i].flag) == 0; i++);
 
-		if (have_flag)
-			xt_xlate_add(xl, ",");
-
-		xt_xlate_add(xl, "%s", tcp_flag_names_xlate[i].name);
+		xt_xlate_add(xl, "%s%s",
+			     have_flag ? "," : "",
+			     tcp_flag_names_xlate[i].name);
 		have_flag = 1;
 
 		flags &= ~tcp_flag_names_xlate[i].flag;
diff --git a/extensions/libxt_time.txlate b/extensions/libxt_time.txlate
index ff4a7b88..2083ab94 100644
--- a/extensions/libxt_time.txlate
+++ b/extensions/libxt_time.txlate
@@ -1,5 +1,5 @@
 iptables-translate -A INPUT -p icmp --icmp-type echo-request -m time --weekdays Sa,Su -j REJECT
-nft add rule ip filter INPUT icmp type echo-request  meta day {6,0} counter reject
+nft add rule ip filter INPUT icmp type echo-request  meta day { 6,0 } counter reject
 
 iptables-translate -A INPUT -p icmp --icmp-type echo-request -m time --timestart 12:00 -j REJECT
 nft add rule ip filter INPUT icmp type echo-request  meta hour "12:00:00"-"23:59:59" counter reject
@@ -20,7 +20,7 @@ iptables-translate -A INPUT -p icmp --icmp-type echo-request -m time --datestart
 nft add rule ip filter INPUT icmp type echo-request meta time "2020-01-29 00:00:00"-"2038-01-19 03:14:07" meta hour "12:00:00"-"23:59:59" counter reject
 
 iptables-translate -A INPUT -p icmp --icmp-type echo-request -m time --datestart 2020-01-29T00:00:00 --timestart 12:00 --timestop 19:00 --weekdays Mon,Tue,Wed,Thu,Fri -j REJECT
-nft add rule ip filter INPUT icmp type echo-request meta time "2020-01-29 00:00:00"-"2038-01-19 03:14:07" meta hour "12:00:00"-"19:00:00" meta day {1,2,3,4,5} counter reject
+nft add rule ip filter INPUT icmp type echo-request meta time "2020-01-29 00:00:00"-"2038-01-19 03:14:07" meta hour "12:00:00"-"19:00:00" meta day { 1,2,3,4,5 } counter reject
 
 iptables-translate -A INPUT -p icmp --icmp-type echo-request -m time --datestart 2020-01-29T00:00:00 --timestart 12:00 --timestop 19:00 ! --weekdays Mon,Tue,Wed,Thu,Fri -j REJECT
-nft add rule ip filter INPUT icmp type echo-request meta time "2020-01-29 00:00:00"-"2038-01-19 03:14:07" meta hour "12:00:00"-"19:00:00" meta day {6,0} counter reject
+nft add rule ip filter INPUT icmp type echo-request meta time "2020-01-29 00:00:00"-"2038-01-19 03:14:07" meta hour "12:00:00"-"19:00:00" meta day { 6,0 } counter reject
diff --git a/include/xtables.h b/include/xtables.h
index 9eba4f61..dad1949e 100644
--- a/include/xtables.h
+++ b/include/xtables.h
@@ -621,8 +621,11 @@ extern const char *xtables_lmap_id2name(const struct xtables_lmap *, int);
 struct xt_xlate *xt_xlate_alloc(int size);
 void xt_xlate_free(struct xt_xlate *xl);
 void xt_xlate_add(struct xt_xlate *xl, const char *fmt, ...) __attribute__((format(printf,2,3)));
+void xt_xlate_add_nospc(struct xt_xlate *xl, const char *fmt, ...) __attribute__((format(printf,2,3)));
 #define xt_xlate_rule_add xt_xlate_add
+#define xt_xlate_rule_add_nospc xt_xlate_add_nospc
 void xt_xlate_set_add(struct xt_xlate *xl, const char *fmt, ...) __attribute__((format(printf,2,3)));
+void xt_xlate_set_add_nospc(struct xt_xlate *xl, const char *fmt, ...) __attribute__((format(printf,2,3)));
 void xt_xlate_add_comment(struct xt_xlate *xl, const char *comment);
 const char *xt_xlate_get_comment(struct xt_xlate *xl);
 void xl_xlate_set_family(struct xt_xlate *xl, uint8_t family);
diff --git a/libxtables/xtables.c b/libxtables/xtables.c
index 479dbae0..e3e444ac 100644
--- a/libxtables/xtables.c
+++ b/libxtables/xtables.c
@@ -2490,16 +2490,39 @@ void xt_xlate_free(struct xt_xlate *xl)
 	free(xl);
 }
 
+static bool isbrace(char c)
+{
+	switch (c) {
+	case '(':
+	case ')':
+	case '{':
+	case '}':
+	case '[':
+	case ']':
+		return true;
+	}
+	return false;
+}
+
 static void __xt_xlate_add(struct xt_xlate *xl, enum xt_xlate_type type,
-			   const char *fmt, va_list ap)
+			   bool space, const char *fmt, va_list ap)
 {
 	struct xt_xlate_buf *buf = &xl->buf[type];
+	char tmpbuf[1024] = "";
 	int len;
 
-	len = vsnprintf(buf->data + buf->off, buf->rem, fmt, ap);
-	if (len < 0 || len >= buf->rem)
+	len = vsnprintf(tmpbuf, 1024, fmt, ap);
+	if (len < 0 || len >= buf->rem - 1)
 		xtables_error(RESOURCE_PROBLEM, "OOM");
 
+	if (space && buf->off &&
+	    !isspace(buf->data[buf->off - 1]) &&
+	    (isalnum(tmpbuf[0]) || isbrace(tmpbuf[0]))) {
+		buf->data[buf->off] = ' ';
+		buf->off++;
+		buf->rem--;
+	}
+	sprintf(buf->data + buf->off, "%s", tmpbuf);
 	buf->rem -= len;
 	buf->off += len;
 }
@@ -2509,7 +2532,16 @@ void xt_xlate_rule_add(struct xt_xlate *xl, const char *fmt, ...)
 	va_list ap;
 
 	va_start(ap, fmt);
-	__xt_xlate_add(xl, XT_XLATE_RULE, fmt, ap);
+	__xt_xlate_add(xl, XT_XLATE_RULE, true, fmt, ap);
+	va_end(ap);
+}
+
+void xt_xlate_rule_add_nospc(struct xt_xlate *xl, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	__xt_xlate_add(xl, XT_XLATE_RULE, false, fmt, ap);
 	va_end(ap);
 }
 
@@ -2518,7 +2550,16 @@ void xt_xlate_set_add(struct xt_xlate *xl, const char *fmt, ...)
 	va_list ap;
 
 	va_start(ap, fmt);
-	__xt_xlate_add(xl, XT_XLATE_SET, fmt, ap);
+	__xt_xlate_add(xl, XT_XLATE_SET, true, fmt, ap);
+	va_end(ap);
+}
+
+void xt_xlate_set_add_nospc(struct xt_xlate *xl, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+	__xt_xlate_add(xl, XT_XLATE_SET, false, fmt, ap);
 	va_end(ap);
 }
 
@@ -2545,7 +2586,12 @@ uint8_t xt_xlate_get_family(struct xt_xlate *xl)
 
 const char *xt_xlate_get(struct xt_xlate *xl)
 {
-	return xl->buf[XT_XLATE_RULE].data;
+	struct xt_xlate_buf *buf = &xl->buf[XT_XLATE_RULE];
+
+	while (buf->off && isspace(buf->data[buf->off - 1]))
+		buf->data[--buf->off] = '\0';
+
+	return buf->data;
 }
 
 const char *xt_xlate_set_get(struct xt_xlate *xl)