This patch adds the extension for the xt_cgroup2 which matches packets
based on the v2 cgroup path of the associated socket.
v2: cgroup2_match->userspacesize and ->save and man page updated as
per Jan.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Daniel Borkmann <dborkman@xxxxxxxxxx>
Cc: Jan Engelhardt <jengelh@xxxxxxx>
---
extensions/libxt_cgroup2.c | 71 +++++++++++++++++++++++++++++++++++
extensions/libxt_cgroup2.man | 24 +++++++++++
include/linux/netfilter/xt_cgroup2.h | 15 +++++++
3 files changed, 110 insertions(+)
--- /dev/null
+++ b/extensions/libxt_cgroup2.c
@@ -0,0 +1,71 @@
+#include <stdio.h>
+#include <mntent.h>
+#include <xtables.h>
+#include <linux/netfilter/xt_cgroup2.h>
+#include <linux/limits.h>
+
+enum {
+ O_CGROUP2_PATH,
+};
+
+static void cgroup2_help(void)
+{
+ printf(
+"cgroup2 match options:\n"
+"[!] --path path path relative to cgroup2 root, recursive match\n");
+}
+
+static const struct xt_option_entry cgroup2_opts[] = {
+ {
+ .name = "path",
+ .id = O_CGROUP2_PATH,
+ .type = XTTYPE_STRING,
+ .flags = XTOPT_INVERT | XTOPT_MAND | XTOPT_PUT,
+ XTOPT_POINTER(struct xt_cgroup2_info, path)
+ },
+ XTOPT_TABLEEND,
+};
+
+static void cgroup2_parse(struct xt_option_call *cb)
+{
+ struct xt_cgroup2_info *info = cb->data;
+
+ xtables_option_parse(cb);
+
+ if (cb->invert)
+ info->invert = true;
+}
+
+static void cgroup2_print(const void *ip, const struct xt_entry_match *match,
+ int numeric)
+{
+ const struct xt_cgroup2_info *info = (void *)match->data;
+
+ printf(" cgroup2 %s%s", info->invert ? "! ":"", info->path);
+}
+
+static void cgroup2_save(const void *ip, const struct xt_entry_match *match)
+{
+ const struct xt_cgroup2_info *info = (void *)match->data;
+
+ printf("%s --path", info->invert ? " !" : "");
+ xtables_save_string(info->path);
+}
+
+static struct xtables_match cgroup2_match = {
+ .family = NFPROTO_UNSPEC,
+ .name = "cgroup2",
+ .version = XTABLES_VERSION,
+ .size = XT_ALIGN(sizeof(struct xt_cgroup2_info)),
+ .userspacesize = offsetof(struct xt_cgroup2_info, priv),
+ .help = cgroup2_help,
+ .print = cgroup2_print,
+ .save = cgroup2_save,
+ .x6_parse = cgroup2_parse,
+ .x6_options = cgroup2_opts,
+};
+
+void _init(void)
+{
+ xtables_register_match(&cgroup2_match);
+}
--- /dev/null
+++ b/extensions/libxt_cgroup2.man
@@ -0,0 +1,24 @@
+.TP
+[\fB!\fP] \fB\-\-path\fP \fIpath\fP
+Match cgroup2 membership.
+
+Each socket is associated with the v2 cgroup of the creating process.
+This matches packets coming from or going to all sockets in the
+sub-hierarchy of the specified path. The path should be relative to
+the root of the cgroup2 hierarchy. Can be used in the OUTPUT and
+INPUT chains to assign particular firewall policies for aggregated
+processes on the system. This allows for more fine-grained firewall
+policies that only match for a subset of the system's processes.
+
+\fBIMPORTANT\fP: when being used in the INPUT chain, the cgroup2
+matcher is currently only of limited functionality, meaning it
+will only match on packets that are processed for local sockets
+through early socket demuxing. Therefore, general usage on the
+INPUT chain is not advised unless the implications are well
+understood.
+.PP
+Example:
+.IP
+iptables \-A OUTPUT \-p tcp \-\-sport 80 \-m cgroup2 ! \-\-path service/http-server \-j DROP
+.PP
+Available since Linux 4.5.
--- /dev/null
+++ b/include/linux/netfilter/xt_cgroup2.h
@@ -0,0 +1,15 @@
+#ifndef _XT_CGROUP2_H
+#define _XT_CGROUP2_H
+
+#include <linux/types.h>
+#include <linux/limits.h>
+
+struct xt_cgroup2_info {
+ char path[PATH_MAX];
+ __u8 invert;
+
+ /* kernel internal data */
+ void *priv __attribute__((aligned(8)));
+};
+
+#endif /* _XT_CGROUP2_H */
--
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