conntrack: snprintf: add labels in hex representation by default

by default, nfct_snprintf will not resolve connlabel names, as they're system specific. This adds a fmt attribute to resolve names accordingly.

output looks like this:
... mark=0 use=1 labels=eth0-in (0),eth1-in (1)
or
<labels>
<label name="eth0-in" bit="0"/>
<label name="eth1-in" bit="1"/>
</labels>

Major stupidity:
As names can be anything, we need to be careful, especially when creating XML output. Only alphanumerical label names are printed at this time.

Else you get
labels=(0), .. or <labels><label name="" bit="0"/> in xml output.

Signed-off-by Florian Westphal <[email protected]>

---
I am interested in feedback wrt.

a) the chosen xml representation
b) wheter it makes sense to limit valid charactes in the label names this way (e.g., should we care? should be disallow that in iptables as well, etc).
c) if this patch makes sense in the first place, e.g, can't use alternate mapping file for labels with nfct_snprintf

 include/internal/internal.h                        |  1 +
 include/internal/prototypes.h                      |  1 +
 .../libnetfilter_conntrack.h                       |  3 +
 src/conntrack/snprintf_default.c                   | 84 +++++++++++++++++++++-
 src/conntrack/snprintf_xml.c                       |  8 ++-
 5 files changed, 93 insertions(+), 4 deletions(-)

include/internal/internal.h +1 -0

index aaf6bd4..a5c7923 100644
@@ -6,6 +6,7 @@
 #ifndef __LIBNETFILTER_CONNTRACK_INTERNAL__
 #define __LIBNETFILTER_CONNTRACK_INTERNAL__
 
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>

include/internal/prototypes.h +1 -0

index cc8de1d..577270b 100644
@@ -16,6 +16,7 @@ int __snprintf_proto(char *buf, unsigned int len, const struct __nfct_tuple *tup
 int __snprintf_conntrack_default(char *buf, unsigned int len, const struct nf_conntrack *ct, const unsigned int msg_type, const unsigned int flags);
 int __snprintf_conntrack_xml(char *buf, unsigned int len, const struct nf_conntrack *ct, const unsigned int msg_type, const unsigned int flags);
 int __snprintf_connlabels(char *buf, unsigned int len, const struct nf_conntrack *ct, const char *prefix, const char *end);
+int __snprintf_connlabels_names(char *buf, unsigned int len, const struct nf_conntrack *ct, const char *prefix, const char *end, bool xml);
 
 enum __nfct_addr {
 	__ADDR_SRC = 0,

include/libnetfilter_conntrack/libnetfilter_conntrack.h +3 -0

index 39dc24c..eedf85e 100644
@@ -389,6 +389,9 @@ enum {
 
 	NFCT_OF_TIMESTAMP_BIT = 3,
 	NFCT_OF_TIMESTAMP = (1 << NFCT_OF_TIMESTAMP_BIT),
+
+	NFCT_OF_CONNLABELS_BIT = 4,
+	NFCT_OF_CONNLABELS = (1 << NFCT_OF_CONNLABELS_BIT),
 };
 
 extern int nfct_snprintf(char *buf, 

src/conntrack/snprintf_default.c +5 -0

index a1edef4..7befbd7 100644
@@ -313,9 +313,89 @@ __snprintf_connlabels(char *buf, unsigned int len,
 	return size;
 }
 
+/*
+ * Labels can have any name, there are no restrictions.
+ * We will only print alpha numerical ones; else parsers
+ * could choke when putinng "&>" and friends into output
+ * (especially when using XML format).  ASCII machines only.

src/conntrack/snprintf_default.c +67 -2

+		if (*label == ' ' || *label == '-')
+			continue;i
+		return false;
+	}
+	return true;
+}
+
+int
+__snprintf_connlabels_names(char *buf, unsigned int len,
+			    const struct nf_conntrack *ct,
+			    const char *prefix, const char *end, bool xml)
+{
+	const struct nfct_bitmask *b = nfct_get_attr(ct, ATTR_CONNLABELS);
+	unsigned int i, max;
+	int ret, size = 0, offset = 0;
+	struct nfct_labelmap *map;
+
+	if (!b)
+		return 0;
+	map = nfct_labelmap_new(NULL);
+	if (!map)
+		return __snprintf_connlabels(buf, len, ct, prefix, end);
+
+	ret = snprintf(buf, len, "%s", prefix);
+	BUFFER_SIZE(ret, size, len, offset);
+	max = nfct_bitmask_maxbit(b);
+	for (i = 0; i <= max && len; i++) {
+		const char *name;
+		if (!nfct_bitmask_test_bit(b, i))
+			continue;
+		name = nfct_labelmap_get_name(map, i);
+		if (!name || !label_is_sane(name))
+			name = "";
+
+		if (xml)
+			ret = snprintf(buf + offset, len, "<label name=\"%s\" ", name);
+		else if (strcmp(name, "") != 0)
+			ret = snprintf(buf + offset, len, "%s ", name);
+		else
+			ret = 0;
+		BUFFER_SIZE(ret, size, len, offset);
+
+		if (xml)
+			ret = snprintf(buf + offset, len, "bit=\"%u\"/>", i);
+		else
+			ret = snprintf(buf + offset, len, "(%u),", i);
+		BUFFER_SIZE(ret, size, len, offset);
+	}
+
+	nfct_labelmap_destroy(map);
+	if (offset && end) {
+		if (!xml) {
+			offset--; /* remove last , */
+			size--;
+		}
+		ret = snprintf(buf + offset, len, "%s", end);
+		BUFFER_SIZE(ret, size, len, offset);
+	}
+	return size;
+}
+
 static int
-__snprintf_clabels(char *buf, unsigned int len, const struct nf_conntrack *ct)
+__snprintf_clabels(char *buf, unsigned int len,
+		   const struct nf_conntrack *ct, bool names)
 {
+	if (names)
+		return  __snprintf_connlabels_names(buf, len, ct,
+					   "labels=", " ", false);
 	return __snprintf_connlabels(buf, len, ct, "labels=", " ");
 }
 

@@ -458,7 +538,7 @@ int __snprintf_conntrack_default(char *buf,
 	}
 
 	if (test_bit(ATTR_CONNLABELS, ct->head.set)) {
-		ret = __snprintf_clabels(buf+offset, len, ct);
+		ret = __snprintf_clabels(buf+offset, len, ct, flags & NFCT_OF_CONNLABELS );
 		BUFFER_SIZE(ret, size, len, offset);
 	}
 

src/conntrack/snprintf_xml.c +6 -2

index f373f5b..1c2440a 100644
@@ -349,8 +349,12 @@ static int __snprintf_tuple_xml(char *buf,
 }
 
 static int
-__snprintf_clabels_xml(char *buf, unsigned int len, const struct nf_conntrack *ct)
+__snprintf_clabels_xml(char *buf, unsigned int len,
+		       const struct nf_conntrack *ct, bool names)
 {
+	if (names)
+		return __snprintf_connlabels_names(buf, len, ct,
+				"<labels>", "</labels>", true);
 	return __snprintf_connlabels(buf, len, ct, "<labels>", "</labels>");
 }
 

@@ -440,7 +444,7 @@ int __snprintf_conntrack_xml(char *buf,
 	}
 
 	if (test_bit(ATTR_CONNLABELS, ct->head.set)) {
-		ret = __snprintf_clabels_xml(buf+offset, len, ct);
+		ret = __snprintf_clabels_xml(buf+offset, len, ct, flags & NFCT_OF_CONNLABELS);
 		BUFFER_SIZE(ret, size, len, offset);
 	}
 

Signature · 6 lines

1.8.1.5

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Quoted 10 lines · Florian Westphal

by default, nfct_snprintf will not resolve connlabel names, as they're system specific. This adds a fmt attribute to resolve names accordingly.

output looks like this:
... mark=0 use=1 labels=eth0-in (0),eth1-in (1)
or
<labels>
<label name="eth0-in" bit="0"/>
<label name="eth1-in" bit="1"/>
</labels>

I think that the bit field is meaningless, so I would just export the strings. I'd use:

<labels>
<label>eth0-in</label>
<label>eth1-in</label>
<labels>

I'd rather use elements, attributes are not easily extensible IMO.

Quoted 4 lines

Major stupidity:
As names can be anything, we need to be careful, especially when creating XML output. Only alphanumerical label names are printed at this time.

Hm, the string is enclosed between commas, isn't that enough to avoid troubles?

Quoted 6 lines

a) the chosen xml representation
b) wheter it makes sense to limit valid charactes in the label names this way (e.g., should we care? should be disallow that in iptables as well, etc).
c) if this patch makes sense in the first place, e.g, can't use alternate mapping file for labels with nfct_snprintf

Regarding c) I think it makes sense. You can add some nfct_set_connlabel_file interface to set where to find it, it's a bit cheating but should resolve the issue.

Quoted 9 lines

src/conntrack/snprintf_default.c +9 -0

+/*
+ * Labels can have any name, there are no restrictions.
+ * We will only print alpha numerical ones; else parsers
+ * could choke when putinng "&>" and friends into output
+ * (especially when using XML format).  ASCII machines only.
+ */
+static bool label_is_sane(const char *label)
+{
+	for (;*label; label++) {

src/conntrack/snprintf_default.c __snprintf_connlabels(char *buf, unsigned int len, · line 330

Quoted 6 lines

src/conntrack/snprintf_default.c +6 -0

+		if (*label >= 'a' && *label <= 'z')
+			continue;
+		if (*label >= 'A' && *label <= 'Z')
+			continue;
+		if (*label >= '0' && *label <= '9')
+			continue;

is isalnum() instead?

Quoted 20 lines · Pablo Neira Ayuso

Quoted 10 lines · Florian Westphal

by default, nfct_snprintf will not resolve connlabel names, as they're system specific. This adds a fmt attribute to resolve names accordingly.

output looks like this:
... mark=0 use=1 labels=eth0-in (0),eth1-in (1)
or
<labels>
<label name="eth0-in" bit="0"/>
<label name="eth1-in" bit="1"/>
</labels>

I think that the bit field is meaningless, so I would just export the strings. I'd use:

<labels>
<label>eth0-in</label>
<label>eth1-in</label>
<labels>

Quoted 1 line

I'd rather use elements, attributes are not easily extensible IMO.

Okay, I'll change it accordingly. In case translation fails i'll put the number in there, so you'd get <label>(42)</label> if bit 42 is set but has no mapping entry.

Quoted 7 lines

Quoted 4 lines

Major stupidity:
As names can be anything, we need to be careful, especially when creating XML output. Only alphanumerical label names are printed at this time.

Hm, the string is enclosed between commas, isn't that enough to avoid troubles?

What if connlabel.conf contains line like
0 foo<bar>&;!"

Quoted 10 lines

Quoted 6 lines

a) the chosen xml representation
b) wheter it makes sense to limit valid charactes in the label names this way (e.g., should we care? should be disallow that in iptables as well, etc).
c) if this patch makes sense in the first place, e.g, can't use alternate mapping file for labels with nfct_snprintf

Regarding c) I think it makes sense. You can add some nfct_set_connlabel_file interface to set where to find it, it's a bit cheating but should resolve the issue.

Yuck ;-)

Lets ignore it for now, adding that would break thread-safety. I guess one alternative would be to add

nfct_labelmap_snprintf(char *buf,

	       	       size_t sz,
		       const struct nfct_labelmap *,
		       const struct nfct_bitmask *, int flags);

When a use case presents itself.

Quoted 9 lines

Quoted 9 lines

src/conntrack/snprintf_default.c +9 -0

+/*
+ * Labels can have any name, there are no restrictions.
+ * We will only print alpha numerical ones; else parsers
+ * could choke when putinng "&>" and friends into output
+ * (especially when using XML format).  ASCII machines only.
+ */
+static bool label_is_sane(const char *label)
+{
+	for (;*label; label++) {

Quoted 8 lines

src/conntrack/snprintf_default.c __snprintf_connlabels(char *buf, unsigned int len, · line 330

Quoted 6 lines

src/conntrack/snprintf_default.c +6 -0

+		if (*label >= 'a' && *label <= 'z')
+			continue;
+		if (*label >= 'A' && *label <= 'Z')
+			continue;
+		if (*label >= '0' && *label <= '9')
+			continue;

is isalnum() instead?

I was intimidated by locale interactions of isalnum...

udp 17 24 [..] dport=62277 mark=0 use=1 labels=0x28000000000000008
or
[..]<mark>0</mark><labels>0x28000000000000008</labels> [..] </meta></flow>

Signed-off-by Florian Westphal <[email protected]>

---
I'm interested if there are any objections on putting
this in by default, one alternative would be to toss this and only print label info with special formating request (see next patch, which adds NFCT_OF_ specifier (which will then print the resovled names instead of bitmask).

I'm not sure about the utility of this without the translation to strings.

Quoted 2 lines · Pablo Neira Ayuso

I'm not sure about the utility of this without the translation to strings.

OK, no objections. Lets just drop it until a use case shows up.