[PATCH iptables] extensions: libxt_quota: Allow setting the remaining quota

Chenbo Feng
2018-10-02T08:04:05Z

From: Chenbo Feng <fengc@google.com>

The current xt_quota module cannot track the current remaining quota
of a specific rule. Everytime an unrelated rule is updated in the same
iptables table, the quota will be reset. This is not a very useful
function for iptables that get changed at run time. This patch fixes the
above problem by adding a new field in the struct that records the
current remaining quota.

Fixed a print out bug in verbose print out wrt. inversion.

Signed-off-by: Chenbo Feng <fengc@google.com>
Suggested-by: Maciej Żenczykowski <maze@google.com>
Reviewed-by: Maciej Żenczykowski <maze@google.com>
---
extensions/libxt_quota.c | 25 +++++++++++++++++++++++--
include/linux/netfilter/xt_quota.h | 8 +++++---
2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/extensions/libxt_quota.c b/extensions/libxt_quota.c
index bad77d2..6371aa0 100644
--- a/extensions/libxt_quota.c
+++ b/extensions/libxt_quota.c
@@ -9,26 +9,36 @@

enum {
O_QUOTA = 0,
+ O_REMAIN = 1,
};

static const struct xt_option_entry quota_opts[] = {
{.name = "quota", .id = O_QUOTA, .type = XTTYPE_UINT64,
.flags = XTOPT_MAND | XTOPT_INVERT | XTOPT_PUT,
XTOPT_POINTER(struct xt_quota_info, quota)},
+ {.name = "remain", .id = O_REMAIN, .type = XTTYPE_UINT64,
+ .flags = XTOPT_PUT, XTOPT_POINTER(struct xt_quota_info, remain)},
XTOPT_TABLEEND,
};

static void quota_help(void)
{
printf("quota match options:\n"
- "[!] --quota quota quota (bytes)\n");
+ "[!] --quota quota quota (bytes)\n"
+ " --remain remain remain (bytes)\n");
}

static void
quota_print(const void *ip, const struct xt_entry_match *match, int numeric)
{
const struct xt_quota_info *q = (const void *)match->data;
+ if (q->flags & XT_QUOTA_INVERT)
+ printf(" !");
printf(" quota: %llu bytes", (unsigned long long)q->quota);
+ if (q->remain) {
+ printf(" remain: %llu bytes",
+ (unsigned long long)q->remain - 1);
+ }
}

static void
@@ -39,6 +49,10 @@ quota_save(const void *ip, const struct xt_entry_match *match)
if (q->flags & XT_QUOTA_INVERT)
printf(" !");
printf(" --quota %llu", (unsigned long long) q->quota);
+ if (q->remain) {
+ printf(" --remain %llu",
+ (unsigned long long) q->remain - 1);
+ }
}

static void quota_parse(struct xt_option_call *cb)
@@ -48,6 +62,8 @@ static void quota_parse(struct xt_option_call *cb)
xtables_option_parse(cb);
if (cb->invert)
info->flags |= XT_QUOTA_INVERT;
+ if (cb->entry->id == O_REMAIN)
+ info->remain++;
}

static int quota_xlate(struct xt_xlate *xl,
@@ -66,7 +82,12 @@ static struct xtables_match quota_match = {
.name = "quota",
.version = XTABLES_VERSION,
.size = XT_ALIGN(sizeof (struct xt_quota_info)),
- .userspacesize = offsetof(struct xt_quota_info, master),
+ /*
+ * This size is only used for rule matching purpose when deleting
+ * rules. The real size copied out from new kernel xt_quota module
+ * is the whole struct xt_quota_info.
+ */
+ .userspacesize = offsetof(struct xt_quota_info, remain),
.help = quota_help,
.print = quota_print,
.save = quota_save,
diff --git a/include/linux/netfilter/xt_quota.h b/include/linux/netfilter/xt_quota.h
index 9314723..d817aab 100644
--- a/include/linux/netfilter/xt_quota.h
+++ b/include/linux/netfilter/xt_quota.h
@@ -14,9 +14,11 @@ struct xt_quota_info {
__u32 flags;
__u32 pad;
__aligned_u64 quota;
-
- /* Used internally by the kernel */
- struct xt_quota_priv *master;
+#ifdef __KERNEL__
+ atomic64_t counter;
+#else
+ __aligned_u64 remain;
+#endif
};

#endif /* _XT_QUOTA_H */
--
2.7.4