On 11/28/22 8:05 AM, Eyal Birger wrote:
This change adds xfrm metadata helpers using the unstable kfunc call
interface for the TC-BPF hooks. This allows steering traffic towards
different IPsec connections based on logic implemented in bpf programs.
This object is built based on the availabilty of BTF debug info.
The metadata percpu dsts used on TX take ownership of the original skb
dsts so that they may be used as part of the xfrm transmittion logic -
e.g. for MTU calculations.
A few quick comments and questions:
Signed-off-by: Eyal Birger <eyal.birger@xxxxxxxxx>
---
include/net/dst_metadata.h | 1 +
include/net/xfrm.h | 20 ++++++++
net/core/dst.c | 4 ++
net/xfrm/Makefile | 6 +++
net/xfrm/xfrm_interface_bpf.c | 92 ++++++++++++++++++++++++++++++++++
Please tag for bpf-next
net/xfrm/xfrm_interface_core.c | 15 ++++++
6 files changed, 138 insertions(+)
create mode 100644 net/xfrm/xfrm_interface_bpf.c
diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h
index a454cf4327fe..1b7fae4c6b24 100644
--- a/include/net/dst_metadata.h
+++ b/include/net/dst_metadata.h
@@ -26,6 +26,7 @@ struct macsec_info {
struct xfrm_md_info {
u32 if_id;
int link;
+ struct dst_entry *dst_orig;
};
struct metadata_dst {
[ ... ]
diff --git a/net/core/dst.c b/net/core/dst.c
index bc9c9be4e080..4c2eb7e56dab 100644
--- a/net/core/dst.c
+++ b/net/core/dst.c
@@ -315,6 +315,8 @@ void metadata_dst_free(struct metadata_dst *md_dst)
#ifdef CONFIG_DST_CACHE
if (md_dst->type == METADATA_IP_TUNNEL)
dst_cache_destroy(&md_dst->u.tun_info.dst_cache);
+ else if (md_dst->type == METADATA_XFRM)
+ dst_release(md_dst->u.xfrm_info.dst_orig);
Why only release dst_orig under CONFIG_DST_CACHE?
#endif
kfree(md_dst);
}
@@ -348,6 +350,8 @@ void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)
if (one_md_dst->type == METADATA_IP_TUNNEL)
dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);
+ else if (one_md_dst->type == METADATA_XFRM)
+ dst_release(one_md_dst->u.xfrm_info.dst_orig);
Same here.
[ ... ]
diff --git a/net/xfrm/xfrm_interface_bpf.c b/net/xfrm/xfrm_interface_bpf.c
new file mode 100644
index 000000000000..d3997ab7cc28
--- /dev/null
+++ b/net/xfrm/xfrm_interface_bpf.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Unstable XFRM Helpers for TC-BPF hook
+ *
+ * These are called from SCHED_CLS BPF programs. Note that it is
+ * allowed to break compatibility for these functions since the interface they
+ * are exposed through to BPF programs is explicitly unstable.
+ */
+
+#include <linux/bpf.h>
+#include <linux/btf_ids.h>
+
+#include <net/dst_metadata.h>
+#include <net/xfrm.h>
+
+struct bpf_xfrm_info {
+ u32 if_id;
+ int link;
+};
+
+static struct metadata_dst __percpu *xfrm_md_dst;
+__diag_push();
+__diag_ignore_all("-Wmissing-prototypes",
+ "Global functions as their definitions will be in xfrm_interface BTF");
+
+__used noinline
+int bpf_skb_get_xfrm_info(struct __sk_buff *skb_ctx, struct bpf_xfrm_info *to)
+{
+ struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+ struct xfrm_md_info *info;
+
+ memset(to, 0, sizeof(*to));
+
+ info = skb_xfrm_md_info(skb);
+ if (!info)
+ return -EINVAL;
+
+ to->if_id = info->if_id;
+ to->link = info->link;
+ return 0;
+}
+
+__used noinline
+int bpf_skb_set_xfrm_info(struct __sk_buff *skb_ctx,
+ const struct bpf_xfrm_info *from)
+{
+ struct sk_buff *skb = (struct sk_buff *)skb_ctx;
+ struct metadata_dst *md_dst;
+ struct xfrm_md_info *info;
+
+ if (unlikely(skb_metadata_dst(skb)))
+ return -EINVAL;
+
+ md_dst = this_cpu_ptr(xfrm_md_dst);
+
+ info = &md_dst->u.xfrm_info;
+ memset(info, 0, sizeof(*info));
+
+ info->if_id = from->if_id;
+ info->link = from->link;
+ info->dst_orig = skb_dst(skb);
However, the dst_orig init is not done under CONFIG_DST_CACHE though...
Also, is it possible that skb->_skb_refdst has SKB_DST_NOREF set and later below
... (contd)
+
+ dst_hold((struct dst_entry *)md_dst);
+ skb_dst_set(skb, (struct dst_entry *)md_dst);
+ return 0;
+}
+
+__diag_pop()
+
+BTF_SET8_START(xfrm_ifc_kfunc_set)
+BTF_ID_FLAGS(func, bpf_skb_get_xfrm_info)
+BTF_ID_FLAGS(func, bpf_skb_set_xfrm_info)
+BTF_SET8_END(xfrm_ifc_kfunc_set)
+
+static const struct btf_kfunc_id_set xfrm_interface_kfunc_set = {
+ .owner = THIS_MODULE,
+ .set = &xfrm_ifc_kfunc_set,
+};
+
+int __init register_xfrm_interface_bpf(void)
+{
+ xfrm_md_dst = metadata_dst_alloc_percpu(0, METADATA_XFRM,
+ GFP_KERNEL);
+ if (!xfrm_md_dst)
+ return -ENOMEM;
+ return register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS,
+ &xfrm_interface_kfunc_set);
Will cleanup_xfrm_interface_bpf() be called during error ?
+}
+
+void __exit cleanup_xfrm_interface_bpf(void)
+{
+ metadata_dst_free_percpu(xfrm_md_dst);
+}
diff --git a/net/xfrm/xfrm_interface_core.c b/net/xfrm/xfrm_interface_core.c
index 5a67b120c4db..1e1e8e965939 100644
--- a/net/xfrm/xfrm_interface_core.c
+++ b/net/xfrm/xfrm_interface_core.c
@@ -396,6 +396,14 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
if_id = md_info->if_id;
fl->flowi_oif = md_info->link;
+ if (md_info->dst_orig) {
+ struct dst_entry *tmp_dst = dst;
+
+ dst = md_info->dst_orig;
+ skb_dst_set(skb, dst);
(contd) ... skb_dst_set() is always called here. (considering there is
skb_dst_set_noref()).
+ md_info->dst_orig = NULL;
+ dst_release(tmp_dst);
+ }
} else {
if_id = xi->p.if_id;
}
@@ -1162,12 +1170,18 @@ static int __init xfrmi_init(void)
if (err < 0)
goto rtnl_link_failed;
+ err = register_xfrm_interface_bpf();
+ if (err < 0)
+ goto kfunc_failed;
+
lwtunnel_encap_add_ops(&xfrmi_encap_ops, LWTUNNEL_ENCAP_XFRM);
xfrm_if_register_cb(&xfrm_if_cb);
return err;
+kfunc_failed:
+ rtnl_link_unregister(&xfrmi_link_ops);
rtnl_link_failed:
xfrmi6_fini();
xfrmi6_failed:
@@ -1183,6 +1197,7 @@ static void __exit xfrmi_fini(void)
{
xfrm_if_unregister_cb();
lwtunnel_encap_del_ops(&xfrmi_encap_ops, LWTUNNEL_ENCAP_XFRM);
+ cleanup_xfrm_interface_bpf();
rtnl_link_unregister(&xfrmi_link_ops);
xfrmi4_fini();
xfrmi6_fini();
