ipv6: sr: introduce seg6local End.BPF action

PATCH Superseded Mathieu Xhonneux 2 participants 9 messages May 17, 2018 – May 20, 2018

Subsystems (9)

Networking Network drivers Kselftest BPF +5 more subsystems

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Mathieu Xhonneux

author

2018-05-17 12:28 UTC #0 lore raw

v6 cover ipv6: sr: introduce seg6local End.BPF action

As of Linux 4.14, it is possible to define advanced local processing for IPv6 packets with a Segment Routing Header through the seg6local LWT infrastructure. This LWT implements the network programming principles defined in the IETF “SRv6 Network Programming” draft.

The implemented operations are generic, and it would be very interesting to be able to implement user-specific seg6local actions, without having to modify the kernel directly. To do so, this patchset adds an End.BPF action to seg6local, powered by some specific Segment Routing-related helpers, which provide SR functionalities that can be applied on the packet. This BPF hook would then allow to implement specific actions at native kernel speed such as OAM features, advanced SR SDN policies, SRv6 actions like Segment Routing Header (SRH) encapsulation depending on the content of the packet, etc.

This patchset is divided in 6 patches, whose main features are :

- A new seg6local action End.BPF with the corresponding new BPF program type BPF_PROG_TYPE_LWT_SEG6LOCAL. Such attached BPF program can be passed to the LWT seg6local through netlink, the same way as the LWT BPF hook operates.
- 3 new BPF helpers for the seg6local BPF hook, allowing to edit/grow/ shrink a SRH and apply on a packet some of the generic SRv6 actions.
- 1 new BPF helper for the LWT BPF IN hook, allowing to add a SRH through encapsulation (via IPv6 encapsulation or inlining if the packet contains already an IPv6 header).

As this patchset adds a new LWT BPF hook, I took into account the result of the discussions when the LWT BPF infrastructure got merged. Hence, the seg6local BPF hook doesn’t allow write access to skb->data directly, only the SRH can be modified through specific helpers, which ensures that the integrity of the packet is maintained.
More details are available in the related patches messages.

The performances of this BPF hook have been assessed with the BPF JIT enabled on a Intel Xeon X3440 processors with 4 cores and 8 threads clocked at 2.53 GHz. No throughput losses are noted with the seg6local BPF hook when the BPF program does nothing (440kpps). Adding a 8-bytes TLV (1 call each to bpf_lwt_seg6_adjust_srh and bpf_lwt_seg6_store_bytes) drops the throughput to 410kpps, and inlining a SRH via bpf_lwt_seg6_action drops the throughput to 420kpps.
All throughputs are stable.

-------
v2: move the SRH integrity state from skb->cb to a per-cpu buffer
v3: - document helpers in man-page style
- fix kbuild bugs
- un-break BPF LWT out hook
- bpf_push_seg6_encap is now static
- preempt_enable is now called when the packet is dropped in input_action_end_bpf
v4: fix kbuild bugs when CONFIG_IPV6=m
v5: fix kbuild sparse warnings when CONFIG_IPV6=m
v6: fix skb pointers-related bugs in helpers

Thanks.

Mathieu Xhonneux (6):
ipv6: sr: make seg6.h includable without IPv6
ipv6: sr: export function lookup_nexthop
bpf: Add IPv6 Segment Routing helpers
bpf: Split lwt inout verifier structures
ipv6: sr: Add seg6local action End.BPF selftests/bpf: test for seg6local End.BPF action

 include/linux/bpf_types.h                         |   5 +-
 include/net/seg6.h                                |   7 +-
 include/net/seg6_local.h                          |  32 ++
 include/uapi/linux/bpf.h                          |  97 ++++-
 include/uapi/linux/seg6_local.h                   |   3 +
 kernel/bpf/verifier.c                             |   1 +
 net/core/filter.c                                 | 393 ++++++++++++++++---
 net/ipv6/Kconfig                                  |   5 +
 net/ipv6/seg6_local.c                             | 180 ++++++++-
 tools/include/uapi/linux/bpf.h                    |  97 ++++-
 tools/lib/bpf/libbpf.c                            |   1 +
 tools/testing/selftests/bpf/Makefile              |   6 +-
 tools/testing/selftests/bpf/bpf_helpers.h         |  12 +
 tools/testing/selftests/bpf/test_lwt_seg6local.c  | 438 ++++++++++++++++++++++
 tools/testing/selftests/bpf/test_lwt_seg6local.sh | 140 +++++++
 15 files changed, 1344 insertions(+), 73 deletions(-)
 create mode 100644 include/net/seg6_local.h
 create mode 100644 tools/testing/selftests/bpf/test_lwt_seg6local.c
 create mode 100755 tools/testing/selftests/bpf/test_lwt_seg6local.sh

Signature · 1 line

2.16.1

Mathieu Xhonneux

author

2018-05-17 12:28 UTC #1 lore raw

PATCH v6 1/6 ipv6: sr: make seg6.h includable without IPv6

include/net/seg6.h cannot be included in a source file if CONFIG_IPV6 is not enabled:
include/net/seg6.h: In function 'seg6_pernet':

Quoted 1 line

Quoted 1 line
include/net/seg6.h:52:14: error: 'struct net' has no member named

                                        'ipv6'; did you mean 'ipv4'?
     return net->ipv6.seg6_data;
                 ^~~~
                 ipv4

This commit makes seg6_pernet return NULL if IPv6 is not compiled, hence allowing seg6.h to be included regardless of the configuration.

Signed-off-by Mathieu Xhonneux <[email protected]>

---
 include/net/seg6.h | 4 ++++
 1 file changed, 4 insertions(+)

include/net/seg6.h +4 -0

index 099bad59dc90..70b4cfac52d7 100644
@@ -49,7 +49,11 @@ struct seg6_pernet_data {
 
 static inline struct seg6_pernet_data *seg6_pernet(struct net *net)
 {
+#if IS_ENABLED(CONFIG_IPV6)
 	return net->ipv6.seg6_data;
+#else
+	return NULL;
+#endif
 }
 
 extern int seg6_init(void);

Signature · 1 line

2.16.1

Mathieu Xhonneux

author

2018-05-17 12:28 UTC #2 lore raw

PATCH v6 2/6 ipv6: sr: export function lookup_nexthop

In reply to Mathieu Xhonneux

The function lookup_nexthop is essential to implement most of the seg6local actions. As we want to provide a BPF helper allowing to apply some of these actions on the packet being processed, the helper should be able to call this function, hence the need to make it public.

Moreover, if one argument is incorrect or if the next hop can not be found, an error should be returned by the BPF helper so the BPF program can adapt its processing of the packet (return an error, properly force the drop, ...). This patch hence makes this function return dst->error to indicate a possible error.

Signed-off-by Mathieu Xhonneux <[email protected]>

Acked-by David Lebrun <[email protected]>

---
 include/net/seg6.h       |  3 ++-
 include/net/seg6_local.h | 24 ++++++++++++++++++++++++
 net/ipv6/seg6_local.c    | 20 +++++++++++---------
 3 files changed, 37 insertions(+), 10 deletions(-)
 create mode 100644 include/net/seg6_local.h

include/net/seg6.h +2 -1

index 70b4cfac52d7..e029e301faa5 100644
@@ -67,5 +67,6 @@ extern bool seg6_validate_srh(struct ipv6_sr_hdr *srh, int len);
 extern int seg6_do_srh_encap(struct sk_buff *skb, struct ipv6_sr_hdr *osrh,
 			     int proto);
 extern int seg6_do_srh_inline(struct sk_buff *skb, struct ipv6_sr_hdr *osrh);
-
+extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
+			       u32 tbl_id);
 #endif

include/net/seg6_local.h new file +24 -0

new file mode 100644
index 000000000000..57498b23085d
@@ -0,0 +1,24 @@
+/*
+ *  SR-IPv6 implementation
+ *
+ *  Authors:
+ *  David Lebrun <[email protected]>
+ *  eBPF support: Mathieu Xhonneux <[email protected]>
+ *
+ *
+ *  This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+#ifndef _NET_SEG6_LOCAL_H
+#define _NET_SEG6_LOCAL_H
+
+#include <linux/net.h>
+#include <linux/ipv6.h>
+
+extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
+			       u32 tbl_id);
+
+#endif

net/ipv6/seg6_local.c +11 -9

index 45722327375a..e9b23fb924ad 100644
@@ -30,6 +30,7 @@
 #ifdef CONFIG_IPV6_SEG6_HMAC
 #include <net/seg6_hmac.h>
 #endif
+#include <net/seg6_local.h>
 #include <linux/etherdevice.h>
 
 struct seg6_local_lwt;

@@ -140,8 +141,8 @@ static void advance_nextseg(struct ipv6_sr_hdr *srh, struct in6_addr *daddr)
 	*daddr = *addr;
 }
 
-static void lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
-			   u32 tbl_id)
+int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
+			u32 tbl_id)
 {
 	struct net *net = dev_net(skb->dev);
 	struct ipv6hdr *hdr = ipv6_hdr(skb);

@@ -187,6 +188,7 @@ static void lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
 
 	skb_dst_drop(skb);
 	skb_dst_set(skb, dst);
+	return dst->error;
 }
 
 /* regular endpoint function */

@@ -200,7 +202,7 @@ static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 
 	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-	lookup_nexthop(skb, NULL, 0);
+	seg6_lookup_nexthop(skb, NULL, 0);
 
 	return dst_input(skb);

@@ -220,7 +222,7 @@ static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 
 	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-	lookup_nexthop(skb, &slwt->nh6, 0);
+	seg6_lookup_nexthop(skb, &slwt->nh6, 0);
 
 	return dst_input(skb);

@@ -239,7 +241,7 @@ static int input_action_end_t(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 
 	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-	lookup_nexthop(skb, NULL, slwt->table);
+	seg6_lookup_nexthop(skb, NULL, slwt->table);
 
 	return dst_input(skb);

@@ -331,7 +333,7 @@ static int input_action_end_dx6(struct sk_buff *skb,
 	if (!ipv6_addr_any(&slwt->nh6))
 		nhaddr = &slwt->nh6;
 
-	lookup_nexthop(skb, nhaddr, 0);
+	seg6_lookup_nexthop(skb, nhaddr, 0);
 
 	return dst_input(skb);
 drop:

@@ -380,7 +382,7 @@ static int input_action_end_dt6(struct sk_buff *skb,
 	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
 		goto drop;
 
-	lookup_nexthop(skb, NULL, slwt->table);
+	seg6_lookup_nexthop(skb, NULL, slwt->table);
 
 	return dst_input(skb);

@@ -406,7 +408,7 @@ static int input_action_end_b6(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
-	lookup_nexthop(skb, NULL, 0);
+	seg6_lookup_nexthop(skb, NULL, 0);
 
 	return dst_input(skb);

@@ -438,7 +440,7 @@ static int input_action_end_b6_encap(struct sk_buff *skb,
 	ipv6_hdr(skb)->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
 	skb_set_transport_header(skb, sizeof(struct ipv6hdr));
 
-	lookup_nexthop(skb, NULL, 0);
+	seg6_lookup_nexthop(skb, NULL, 0);
 
 	return dst_input(skb);

Signature · 1 line

2.16.1

Mathieu Xhonneux

author

2018-05-17 12:28 UTC #3 lore raw

PATCH v6 3/6 bpf: Add IPv6 Segment Routing helpers

In reply to Mathieu Xhonneux

The BPF seg6local hook should be powerful enough to enable users to implement most of the use-cases one could think of. After some thinking, we figured out that the following actions should be possible on a SRv6 packet, requiring 3 specific helpers :
- bpf_lwt_seg6_store_bytes: Modify non-sensitive fields of the SRH
- bpf_lwt_seg6_adjust_srh: Allow to grow or shrink a SRH (to add/delete TLVs)
- bpf_lwt_seg6_action: Apply some SRv6 network programming actions (specifically End.X, End.T, End.B6 and End.B6.Encap)

The specifications of these helpers are provided in the patch (see include/uapi/linux/bpf.h).

The non-sensitive fields of the SRH are the following : flags, tag and TLVs. The other fields can not be modified, to maintain the SRH integrity. Flags, tag and TLVs can easily be modified as their validity can be checked afterwards via seg6_validate_srh. It is not allowed to modify the segments directly. If one wants to add segments on the path, he should stack a new SRH using the End.B6 action via bpf_lwt_seg6_action.

Growing, shrinking or editing TLVs via the helpers will flag the SRH as invalid, and it will have to be re-validated before re-entering the IPv6 layer. This flag is stored in a per-CPU buffer, along with the current header length in bytes.

Storing the SRH len in bytes in the control block is mandatory when using bpf_lwt_seg6_adjust_srh. The Header Ext. Length field contains the SRH len rounded to 8 bytes (a padding TLV can be inserted to ensure the 8-bytes boundary). When adding/deleting TLVs within the BPF program, the SRH may temporary be in an invalid state where its length cannot be rounded to 8 bytes without remainder, hence the need to store the length in bytes separately. The caller of the BPF program can then ensure that the SRH's final length is valid using this value. Again, a final SRH modified by a BPF program which doesn’t respect the 8-bytes boundary will be discarded as it will be considered as invalid.

Finally, a fourth helper is provided, bpf_lwt_push_encap, which is available from the LWT BPF IN hook, but not from the seg6local BPF one. This helper allows to encapsulate a Segment Routing Header (either with a new outer IPv6 header, or by inlining it directly in the existing IPv6 header) into a non-SRv6 packet. This helper is required if we want to offer the possibility to dynamically encapsulate a SRH for non-SRv6 packet, as the BPF seg6local hook only works on traffic already containing a SRH. This is the BPF equivalent of the seg6 LWT infrastructure, which achieves the same purpose but with a static SRH per route.

These helpers require CONFIG_IPV6=y (and not =m).

Signed-off-by Mathieu Xhonneux <[email protected]>

Acked-by David Lebrun <[email protected]>

---
 include/net/seg6_local.h |   8 ++
 include/uapi/linux/bpf.h |  96 +++++++++++++++-
 net/core/filter.c        | 285 +++++++++++++++++++++++++++++++++++++++++++----
 net/ipv6/Kconfig         |   5 +
 net/ipv6/seg6_local.c    |   2 +
 5 files changed, 372 insertions(+), 24 deletions(-)

include/net/seg6_local.h +8 -0

index 57498b23085d..661fd5b4d3e0 100644
@@ -15,10 +15,18 @@
 #ifndef _NET_SEG6_LOCAL_H
 #define _NET_SEG6_LOCAL_H
 
+#include <linux/percpu.h>
 #include <linux/net.h>
 #include <linux/ipv6.h>
 
 extern int seg6_lookup_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
 			       u32 tbl_id);
 
+struct seg6_bpf_srh_state {
+	bool valid;
+	u16 hdrlen;
+};
+
+DECLARE_PER_CPU(struct seg6_bpf_srh_state, seg6_bpf_srh_states);
+
 #endif

include/uapi/linux/bpf.h +95 -1

114 lines not on this page · raw message

net/core/filter.c +262 ~~-23~~

309 lines not on this page · raw message

net/ipv6/Kconfig +5 -0

index 11e4e80cf7e9..0eff75525da1 100644
@@ -329,4 +329,9 @@ config IPV6_SEG6_HMAC
 
 	  If unsure, say N.
 
+config IPV6_SEG6_BPF
+	def_bool y
+	depends on IPV6_SEG6_LWTUNNEL
+	depends on IPV6 = y
+
 endif # IPV6

net/ipv6/seg6_local.c +2 -0

index e9b23fb924ad..ae68c1ef8fb0 100644
@@ -449,6 +449,8 @@ static int input_action_end_b6_encap(struct sk_buff *skb,
 	return err;
 }
 
+DEFINE_PER_CPU(struct seg6_bpf_srh_state, seg6_bpf_srh_states);
+
 static struct seg6_action_desc seg6_action_table[] = {
 	{
 		.action		= SEG6_LOCAL_ACTION_END,

Signature · 1 line

2.16.1

Mathieu Xhonneux

author

2018-05-17 12:28 UTC #4 lore raw

PATCH v6 4/6 bpf: Split lwt inout verifier structures

In reply to Mathieu Xhonneux

The new bpf_lwt_push_encap helper should only be accessible within the LWT BPF IN hook, and not the OUT one, as this may lead to a skb under panic.

At the moment, both LWT BPF IN and OUT share the same list of helpers, whose calls are authorized by the verifier. This patch separates the verifier ops for the IN and OUT hooks, and allows the IN hook to call the bpf_lwt_push_encap helper.

This patch is also the occasion to put all lwt_*_func_proto functions together for clarity. At the moment, socks_op_func_proto is in the middle of lwt_inout_func_proto and lwt_xmit_func_proto.

Signed-off-by Mathieu Xhonneux <[email protected]>

Acked-by David Lebrun <[email protected]>

---
 include/linux/bpf_types.h |  4 +--
 net/core/filter.c         | 83 +++++++++++++++++++++++++++++------------------
 2 files changed, 54 insertions(+), 33 deletions(-)

include/linux/bpf_types.h +2 -2

index b67f8793de0d..aa5c8b878474 100644
@@ -9,8 +9,8 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_XDP, xdp)
 BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SKB, cg_skb)
 BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCK, cg_sock)
 BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCK_ADDR, cg_sock_addr)
-BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_IN, lwt_inout)
-BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_OUT, lwt_inout)
+BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_IN, lwt_in)
+BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_OUT, lwt_out)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_XMIT, lwt_xmit)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SOCK_OPS, sock_ops)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_SKB, sk_skb)

net/core/filter.c +52 ~~-31~~

111 lines not on this page · raw message

Signature · 1 line

2.16.1

Mathieu Xhonneux

author

2018-05-17 12:28 UTC #5 lore raw

PATCH v6 5/6 ipv6: sr: Add seg6local action End.BPF

In reply to Mathieu Xhonneux

This patch adds the End.BPF action to the LWT seg6local infrastructure. This action works like any other seg6local End action, meaning that an IPv6 header with SRH is needed, whose DA has to be equal to the SID of the action. It will also advance the SRH to the next segment, the BPF program does not have to take care of this.

Since the BPF program may not be a source of instability in the kernel, it is important to ensure that the integrity of the packet is maintained before yielding it back to the IPv6 layer. The hook hence keeps track if the SRH has been altered through the helpers, and re-validates its content if needed with seg6_validate_srh. The state kept for validation is stored in a per-CPU buffer. The BPF program is not allowed to directly write into the packet, and only some fields of the SRH can be altered through the helper bpf_lwt_seg6_store_bytes.

Performances profiling has shown that the SRH re-validation does not induce a significant overhead. If the altered SRH is deemed as invalid, the packet is dropped.

This validation is also done before executing any action through bpf_lwt_seg6_action, and will not be performed again if the SRH is not modified after calling the action.

The BPF program may return 3 types of return codes:
- BPF_OK: the End.BPF action will look up the next destination through seg6_lookup_nexthop.
- BPF_REDIRECT: if an action has been executed through the bpf_lwt_seg6_action helper, the BPF program should return this value, as the skb's destination is already set and the default lookup should not be performed.
- BPF_DROP : the packet will be dropped.

Signed-off-by Mathieu Xhonneux <[email protected]>

Acked-by David Lebrun <[email protected]>

---
 include/linux/bpf_types.h       |   1 +
 include/uapi/linux/bpf.h        |   1 +
 include/uapi/linux/seg6_local.h |   3 +
 kernel/bpf/verifier.c           |   1 +
 net/core/filter.c               |  25 +++++++
 net/ipv6/seg6_local.c           | 158 +++++++++++++++++++++++++++++++++++++++-
 tools/lib/bpf/libbpf.c          |   1 +
 7 files changed, 187 insertions(+), 3 deletions(-)

include/linux/bpf_types.h +1 -0

index aa5c8b878474..b161e506dcfc 100644
@@ -12,6 +12,7 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_CGROUP_SOCK_ADDR, cg_sock_addr)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_IN, lwt_in)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_OUT, lwt_out)
 BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_XMIT, lwt_xmit)
+BPF_PROG_TYPE(BPF_PROG_TYPE_LWT_SEG6LOCAL, lwt_seg6local)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SOCK_OPS, sock_ops)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_SKB, sk_skb)
 BPF_PROG_TYPE(BPF_PROG_TYPE_SK_MSG, sk_msg)

include/uapi/linux/bpf.h +1 -0

index 37f098ca822b..e8efb12d0a7d 100644
@@ -141,6 +141,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_MSG,
 	BPF_PROG_TYPE_RAW_TRACEPOINT,
 	BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	BPF_PROG_TYPE_LWT_SEG6LOCAL,
 };
 
 enum bpf_attach_type {

include/uapi/linux/seg6_local.h +3 -0

index ef2d8c3e76c1..aadcc11fb918 100644
@@ -25,6 +25,7 @@ enum {
 	SEG6_LOCAL_NH6,
 	SEG6_LOCAL_IIF,
 	SEG6_LOCAL_OIF,
+	SEG6_LOCAL_BPF,
 	__SEG6_LOCAL_MAX,
 };
 #define SEG6_LOCAL_MAX (__SEG6_LOCAL_MAX - 1)

@@ -59,6 +60,8 @@ enum {
 	SEG6_LOCAL_ACTION_END_AS	= 13,
 	/* forward to SR-unaware VNF with masquerading */
 	SEG6_LOCAL_ACTION_END_AM	= 14,
+	/* custom BPF action */
+	SEG6_LOCAL_ACTION_END_BPF	= 15,
 
 	__SEG6_LOCAL_ACTION_MAX,
 };

kernel/bpf/verifier.c +1 -0

index a9e4b1372da6..390142d62ba1 100644
@@ -1262,6 +1262,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
 	switch (env->prog->type) {
 	case BPF_PROG_TYPE_LWT_IN:
 	case BPF_PROG_TYPE_LWT_OUT:
+	case BPF_PROG_TYPE_LWT_SEG6LOCAL:
 		/* dst_input() and dst_output() can't write for now */
 		if (t == BPF_WRITE)
 			return false;

net/core/filter.c +25 -0

index 39641ea567b4..8cf0065107a3 100644
@@ -4893,6 +4893,21 @@ lwt_xmit_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 	}
 }
 
+static const struct bpf_func_proto *
+lwt_seg6local_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_lwt_seg6_store_bytes:
+		return &bpf_lwt_seg6_store_bytes_proto;
+	case BPF_FUNC_lwt_seg6_action:
+		return &bpf_lwt_seg6_action_proto;
+	case BPF_FUNC_lwt_seg6_adjust_srh:
+		return &bpf_lwt_seg6_adjust_srh_proto;
+	default:
+		return lwt_out_func_proto(func_id, prog);
+	}
+}
+
 static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type,
 				    const struct bpf_prog *prog,
 				    struct bpf_insn_access_aux *info)

@@ -6493,6 +6508,16 @@ const struct bpf_prog_ops lwt_xmit_prog_ops = {
 	.test_run		= bpf_prog_test_run_skb,
 };
 
+const struct bpf_verifier_ops lwt_seg6local_verifier_ops = {
+	.get_func_proto		= lwt_seg6local_func_proto,
+	.is_valid_access	= lwt_is_valid_access,
+	.convert_ctx_access	= bpf_convert_ctx_access,
+};
+
+const struct bpf_prog_ops lwt_seg6local_prog_ops = {
+	.test_run		= bpf_prog_test_run_skb,
+};
+
 const struct bpf_verifier_ops cg_sock_verifier_ops = {
 	.get_func_proto		= sock_filter_func_proto,
 	.is_valid_access	= sock_filter_is_valid_access,

net/ipv6/seg6_local.c +155 -3

225 lines not on this page · raw message

tools/lib/bpf/libbpf.c +1 -0

index 3dbe217bf23e..a29fed1dfce2 100644
@@ -1456,6 +1456,7 @@ static bool bpf_prog_type__needs_kver(enum bpf_prog_type type)
 	case BPF_PROG_TYPE_LWT_IN:
 	case BPF_PROG_TYPE_LWT_OUT:
 	case BPF_PROG_TYPE_LWT_XMIT:
+	case BPF_PROG_TYPE_LWT_SEG6LOCAL:
 	case BPF_PROG_TYPE_SOCK_OPS:
 	case BPF_PROG_TYPE_SK_SKB:
 	case BPF_PROG_TYPE_CGROUP_DEVICE:

Signature · 1 line

2.16.1

Daniel Borkmann

maintainer

2018-05-18 20:24 UTC #6 lore raw

Re: [PATCH bpf-next v6 5/6] ipv6: sr: Add seg6local action End.BPF

Quoted 34 lines · Mathieu Xhonneux

This patch adds the End.BPF action to the LWT seg6local infrastructure. This action works like any other seg6local End action, meaning that an IPv6 header with SRH is needed, whose DA has to be equal to the SID of the action. It will also advance the SRH to the next segment, the BPF program does not have to take care of this.
Since the BPF program may not be a source of instability in the kernel, it is important to ensure that the integrity of the packet is maintained before yielding it back to the IPv6 layer. The hook hence keeps track if the SRH has been altered through the helpers, and re-validates its content if needed with seg6_validate_srh. The state kept for validation is stored in a per-CPU buffer. The BPF program is not allowed to directly write into the packet, and only some fields of the SRH can be altered through the helper bpf_lwt_seg6_store_bytes.
Performances profiling has shown that the SRH re-validation does not induce a significant overhead. If the altered SRH is deemed as invalid, the packet is dropped.
This validation is also done before executing any action through bpf_lwt_seg6_action, and will not be performed again if the SRH is not modified after calling the action.
The BPF program may return 3 types of return codes:
- BPF_OK: the End.BPF action will look up the next destination through seg6_lookup_nexthop.
- BPF_REDIRECT: if an action has been executed through the bpf_lwt_seg6_action helper, the BPF program should return this value, as the skb's destination is already set and the default lookup should not be performed.
- BPF_DROP : the packet will be dropped.
Signed-off-by Mathieu Xhonneux <[email protected]>
Acked-by David Lebrun <[email protected]>

[...]

Quoted 34 lines

static struct seg6_action_desc seg6_action_table[] = {

net/ipv6/seg6_local.c +11 -1

 	{
 		.action		= SEG6_LOCAL_ACTION_END,

@@ -497,7 +568,13 @@ static struct seg6_action_desc seg6_action_table[] = {
 		.attrs		= (1 << SEG6_LOCAL_SRH),
 		.input		= input_action_end_b6_encap,
 		.static_headroom	= sizeof(struct ipv6hdr),
-	}
+	},
+	{
+		.action		= SEG6_LOCAL_ACTION_END_BPF,
+		.attrs		= (1 << SEG6_LOCAL_BPF),
+		.input		= input_action_end_bpf,
+	},
+
 };
 
 static struct seg6_action_desc *__get_action_desc(int action)

@@ -542,6 +619,7 @@ static const struct nla_policy seg6_local_policy[SEG6_LOCAL_MAX + 1] = {
 				    .len = sizeof(struct in6_addr) },
 	[SEG6_LOCAL_IIF]	= { .type = NLA_U32 },
 	[SEG6_LOCAL_OIF]	= { .type = NLA_U32 },
+	[SEG6_LOCAL_BPF]	= { .type = NLA_NESTED },
 };
 
 static int parse_nla_srh(struct nlattr **attrs, struct seg6_local_lwt *slwt)

@@ -719,6 +797,71 @@ static int cmp_nla_oif(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
 	return 0;
 }
 
+#define MAX_PROG_NAME 256
+static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
+	[LWT_BPF_PROG_FD]   = { .type = NLA_U32, },

Quoted 1 line

From UAPI point of view, I wouldn't name it LWT_BPF_PROG_FD but rather something like

LWT_BPF_PROG for example. That way, the setup can contain the fd number, but on the dump you can put the prog->aux->id in there so that prog lookup can be done again.

Quoted 17 lines

net/ipv6/seg6_local.c +17 -0

+	[LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
+				.len = MAX_PROG_NAME },
+};
+
+static int parse_nla_bpf(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+{
+	struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
+	struct bpf_prog *p;
+	int ret;
+	u32 fd;
+
+	ret = nla_parse_nested(tb, LWT_BPF_PROG_MAX, attrs[SEG6_LOCAL_BPF],
+			       bpf_prog_policy, NULL);
+	if (ret < 0)
+		return ret;
+
+	if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])

net/ipv6/seg6_local.c static int cmp_nla_oif(struct seg6_local_lwt *a, struct seg6_local_lwt *b) · line 829

Quoted 10 lines

net/ipv6/seg6_local.c +10 -0

+		return -EINVAL;
+
+	slwt->bpf.name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_KERNEL);
+	if (!slwt->bpf.name)
+		return -ENOMEM;
+
+	fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
+	p = bpf_prog_get_type(fd, BPF_PROG_TYPE_LWT_SEG6LOCAL);
+	if (IS_ERR(p))
+		return PTR_ERR(p);

Here in the above error path is definitely a bug in that you don't free the prior allocated slwt->bpf.name from nla_memdup().

Also when you destroy the struct seg6_local_lwt object, what I'm not getting is where you drop the prog reference again and free slwt->bpf.name there?

Quoted 83 lines

net/ipv6/seg6_local.c +45 -1

+
+	slwt->bpf.prog = p;
+
+	return 0;
+}
+
+static int put_nla_bpf(struct sk_buff *skb, struct seg6_local_lwt *slwt)
+{
+	struct nlattr *nest;
+
+	if (!slwt->bpf.prog)
+		return 0;
+
+	nest = nla_nest_start(skb, SEG6_LOCAL_BPF);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (slwt->bpf.name &&
+	    nla_put_string(skb, LWT_BPF_PROG_NAME, slwt->bpf.name))
+		return -EMSGSIZE;
+
+	return nla_nest_end(skb, nest);
+}
+
+static int cmp_nla_bpf(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
+{
+	if (!a->bpf.name && !b->bpf.name)
+		return 0;
+
+	if (!a->bpf.name || !b->bpf.name)
+		return 1;
+
+	return strcmp(a->bpf.name, b->bpf.name);
+}
+
 struct seg6_action_param {
 	int (*parse)(struct nlattr **attrs, struct seg6_local_lwt *slwt);
 	int (*put)(struct sk_buff *skb, struct seg6_local_lwt *slwt);

@@ -749,6 +892,11 @@ static struct seg6_action_param seg6_action_params[SEG6_LOCAL_MAX + 1] = {
 	[SEG6_LOCAL_OIF]	= { .parse = parse_nla_oif,
 				    .put = put_nla_oif,
 				    .cmp = cmp_nla_oif },
+
+	[SEG6_LOCAL_BPF]	= { .parse = parse_nla_bpf,
+				    .put = put_nla_bpf,
+				    .cmp = cmp_nla_bpf },
+
 };
 
 static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt)

@@ -797,7 +945,6 @@ static int seg6_local_build_state(struct nlattr *nla, unsigned int family,
 
 	err = nla_parse_nested(tb, SEG6_LOCAL_MAX, nla, seg6_local_policy,
 			       extack);
-
 	if (err < 0)
 		return err;

@@ -886,6 +1033,11 @@ static int seg6_local_get_encap_size(struct lwtunnel_state *lwt)
 	if (attrs & (1 << SEG6_LOCAL_OIF))
 		nlsize += nla_total_size(4);
 
+	if (attrs & (1 << SEG6_LOCAL_BPF))
+		nlsize += nla_total_size(sizeof(struct nlattr)) +
+		       nla_total_size(MAX_PROG_NAME) +
+		       nla_total_size(4);
+
 	return nlsize;
 }

tools/lib/bpf/libbpf.c +1 -0

index 3dbe217bf23e..a29fed1dfce2 100644
@@ -1456,6 +1456,7 @@ static bool bpf_prog_type__needs_kver(enum bpf_prog_type type)
 	case BPF_PROG_TYPE_LWT_IN:
 	case BPF_PROG_TYPE_LWT_OUT:
 	case BPF_PROG_TYPE_LWT_XMIT:
+	case BPF_PROG_TYPE_LWT_SEG6LOCAL:
 	case BPF_PROG_TYPE_SOCK_OPS:
 	case BPF_PROG_TYPE_SK_SKB:
 	case BPF_PROG_TYPE_CGROUP_DEVICE:

Mathieu Xhonneux

author

2018-05-20 11:21 UTC #7 lore raw

Re: [PATCH bpf-next v6 5/6] ipv6: sr: Add seg6local action End.BPF

2018-05-18 21:24 GMT+01:00 Daniel Borkmann <[email protected]>:

Quoted 7 lines

net/ipv6/seg6_local.c static int cmp_nla_oif(struct seg6_local_lwt *a, struct seg6_local_lwt *b) · line 802
Quoted 3 lines
net/ipv6/seg6_local.c +3 -0
+#define MAX_PROG_NAME 256
+static const struct nla_policy bpf_prog_policy[LWT_BPF_PROG_MAX + 1] = {
+     [LWT_BPF_PROG_FD]   = { .type = NLA_U32, },
From UAPI point of view, I wouldn't name it LWT_BPF_PROG_FD but rather something like LWT_BPF_PROG for example. That way, the setup can contain the fd number, but on the dump you can put the prog->aux->id in there so that prog lookup can be done again.

Good idea.

Quoted 22 lines

net/ipv6/seg6_local.c +22 -0

+     [LWT_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
+                             .len = MAX_PROG_NAME },
+};
+
+static int parse_nla_bpf(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+{
+     struct nlattr *tb[LWT_BPF_PROG_MAX + 1];
+     struct bpf_prog *p;
+     int ret;
+     u32 fd;
+
+     ret = nla_parse_nested(tb, LWT_BPF_PROG_MAX, attrs[SEG6_LOCAL_BPF],
+                            bpf_prog_policy, NULL);
+     if (ret < 0)
+             return ret;
+
+     if (!tb[LWT_BPF_PROG_FD] || !tb[LWT_BPF_PROG_NAME])
+             return -EINVAL;
+
+     slwt->bpf.name = nla_memdup(tb[LWT_BPF_PROG_NAME], GFP_KERNEL);
+     if (!slwt->bpf.name)
+             return -ENOMEM;

Quoted 8 lines

net/ipv6/seg6_local.c static int cmp_nla_oif(struct seg6_local_lwt *a, struct seg6_local_lwt *b) · line 829
Quoted 5 lines
net/ipv6/seg6_local.c +5 -0
+
+     fd = nla_get_u32(tb[LWT_BPF_PROG_FD]);
+     p = bpf_prog_get_type(fd, BPF_PROG_TYPE_LWT_SEG6LOCAL);
+     if (IS_ERR(p))
+             return PTR_ERR(p);
Here in the above error path is definitely a bug in that you don't free the prior allocated slwt->bpf.name from nla_memdup().

Indeed, I took this part from the lwt bpf infrastructure. I sent a patch to fix it there too.

Quoted 2 lines

Also when you destroy the struct seg6_local_lwt object, what I'm not getting is where you drop the prog reference again and free slwt->bpf.name there?

I totally missed this. Sending a v7 with all of this fixed.

Thanks for your comments !

Mathieu Xhonneux

author

2018-05-17 12:28 UTC #8 lore raw

PATCH v6 6/6 selftests/bpf: test for seg6local End.BPF action

In reply to Mathieu Xhonneux

Add a new test for the seg6local End.BPF action. The following helpers are also tested:

- bpf_lwt_push_encap within the LWT BPF IN hook
- bpf_lwt_seg6_action
- bpf_lwt_seg6_adjust_srh
- bpf_lwt_seg6_store_bytes

A chain of End.BPF actions is built. The SRH is injected through a LWT BPF IN hook before the chain. Each End.BPF action validates the previous one, otherwise the packet is dropped.
The test succeeds if the last node in the chain receives the packet and the UDP datagram contained can be retrieved from userspace.

Signed-off-by Mathieu Xhonneux <[email protected]>

---
 tools/include/uapi/linux/bpf.h                    |  97 ++++-
 tools/testing/selftests/bpf/Makefile              |   6 +-
 tools/testing/selftests/bpf/bpf_helpers.h         |  12 +
 tools/testing/selftests/bpf/test_lwt_seg6local.c  | 438 ++++++++++++++++++++++
 tools/testing/selftests/bpf/test_lwt_seg6local.sh | 140 +++++++
 5 files changed, 690 insertions(+), 3 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/test_lwt_seg6local.c
 create mode 100755 tools/testing/selftests/bpf/test_lwt_seg6local.sh

tools/include/uapi/linux/bpf.h +96 -1

index d94d333a8225..e8efb12d0a7d 100644
@@ -141,6 +141,7 @@ enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_MSG,
 	BPF_PROG_TYPE_RAW_TRACEPOINT,
 	BPF_PROG_TYPE_CGROUP_SOCK_ADDR,
+	BPF_PROG_TYPE_LWT_SEG6LOCAL,
 };
 
 enum bpf_attach_type {

@@ -1902,6 +1903,90 @@ union bpf_attr {
  *		egress otherwise). This is the only flag supported for now.
  *	Return
  *		**SK_PASS** on success, or **SK_DROP** on error.
+ *
+ * int bpf_lwt_push_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len)
+ *	Description
+ *		Encapsulate the packet associated to *skb* within a Layer 3
+ *		protocol header. This header is provided in the buffer at
+ *		address *hdr*, with *len* its size in bytes. *type* indicates
+ *		the protocol of the header and can be one of:
+ *
+ *		**BPF_LWT_ENCAP_SEG6**
+ *			IPv6 encapsulation with Segment Routing Header
+ *			(**struct ipv6_sr_hdr**). *hdr* only contains the SRH,
+ *			the IPv6 header is computed by the kernel.
+ *		**BPF_LWT_ENCAP_SEG6_INLINE**
+ *			Only works if *skb* contains an IPv6 packet. Insert a
+ *			Segment Routing Header (**struct ipv6_sr_hdr**) inside
+ *			the IPv6 header.
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_lwt_seg6_store_bytes(struct sk_buff *skb, u32 offset, const void *from, u32 len)
+ *	Description
+ *		Store *len* bytes from address *from* into the packet
+ *		associated to *skb*, at *offset*. Only the flags, tag and TLVs
+ *		inside the outermost IPv6 Segment Routing Header can be
+ *		modified through this helper.
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_lwt_seg6_adjust_srh(struct sk_buff *skb, u32 offset, s32 delta)
+ *	Description
+ *		Adjust the size allocated to TLVs in the outermost IPv6
+ *		Segment Routing Header contained in the packet associated to
+ *		*skb*, at position *offset* by *delta* bytes. Only offsets
+ *		after the segments are accepted. *delta* can be as well
+ *		positive (growing) as negative (shrinking).
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
+ *
+ * int bpf_lwt_seg6_action(struct sk_buff *skb, u32 action, void *param, u32 param_len)
+ *	Description
+ *		Apply an IPv6 Segment Routing action of type *action* to the
+ *		packet associated to *skb*. Each action takes a parameter
+ *		contained at address *param*, and of length *param_len* bytes.
+ *		*action* can be one of:
+ *
+ *		**SEG6_LOCAL_ACTION_END_X**
+ *			End.X action: Endpoint with Layer-3 cross-connect.
+ *			Type of *param*: **struct in6_addr**.
+ *		**SEG6_LOCAL_ACTION_END_T**
+ *			End.T action: Endpoint with specific IPv6 table lookup.
+ *			Type of *param*: **int**.
+ *		**SEG6_LOCAL_ACTION_END_B6**
+ *			End.B6 action: Endpoint bound to an SRv6 policy.
+ *			Type of param: **struct ipv6_sr_hdr**.
+ *		**SEG6_LOCAL_ACTION_END_B6_ENCAP**
+ *			End.B6.Encap action: Endpoint bound to an SRv6
+ *			encapsulation policy.
+ *			Type of param: **struct ipv6_sr_hdr**.
+ *
+ * 		A call to this helper is susceptible to change the underlaying
+ * 		packet buffer. Therefore, at load time, all checks on pointers
+ * 		previously done by the verifier are invalidated and must be
+ * 		performed again, if the helper is used in combination with
+ * 		direct packet access.
+ *	Return
+ * 		0 on success, or a negative error in case of failure.
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\

@@ -1976,7 +2061,11 @@ union bpf_attr {
 	FN(fib_lookup),			\
 	FN(sock_hash_update),		\
 	FN(msg_redirect_hash),		\
-	FN(sk_redirect_hash),
+	FN(sk_redirect_hash),		\
+	FN(lwt_push_encap),		\
+	FN(lwt_seg6_store_bytes),	\
+	FN(lwt_seg6_adjust_srh),	\
+	FN(lwt_seg6_action),
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
  * function eBPF program intends to call

@@ -2043,6 +2132,12 @@ enum bpf_hdr_start_off {
 	BPF_HDR_START_NET,
 };
 
+/* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */
+enum bpf_lwt_encap_mode {
+	BPF_LWT_ENCAP_SEG6,
+	BPF_LWT_ENCAP_SEG6_INLINE
+};
+
 /* user accessible mirror of in-kernel sk_buff.
  * new fields can only be added to the end of this structure
  */

tools/testing/selftests/bpf/Makefile +4 -2

index 1eb0fa2aba92..b6222b3f8fab 100644
@@ -33,7 +33,8 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
 	sample_map_ret0.o test_tcpbpf_kern.o test_stacktrace_build_id.o \
 	sockmap_tcp_msg_prog.o connect4_prog.o connect6_prog.o test_adjust_tail.o \
 	test_btf_haskv.o test_btf_nokv.o test_sockmap_kern.o test_tunnel_kern.o \
-	test_get_stack_rawtp.o test_sockmap_kern.o test_sockhash_kern.o
+	test_get_stack_rawtp.o test_sockmap_kern.o test_sockhash_kern.o \
+	test_lwt_seg6local.o
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \

@@ -42,7 +43,8 @@ TEST_PROGS := test_kmod.sh \
 	test_xdp_meta.sh \
 	test_offload.py \
 	test_sock_addr.sh \
-	test_tunnel.sh
+	test_tunnel.sh \
+	test_lwt_seg6local.sh
 
 # Compile but not part of 'make run_tests'
 TEST_GEN_PROGS_EXTENDED = test_libbpf_open test_sock_addr

tools/testing/selftests/bpf/bpf_helpers.h +12 -0

index 8f143dfb3700..334d3e8c5e89 100644
@@ -114,6 +114,18 @@ static int (*bpf_get_stack)(void *ctx, void *buf, int size, int flags) =
 static int (*bpf_fib_lookup)(void *ctx, struct bpf_fib_lookup *params,
 			     int plen, __u32 flags) =
 	(void *) BPF_FUNC_fib_lookup;
+static int (*bpf_lwt_push_encap)(void *ctx, unsigned int type, void *hdr,
+				 unsigned int len) =
+	(void *) BPF_FUNC_lwt_push_encap;
+static int (*bpf_lwt_seg6_store_bytes)(void *ctx, unsigned int offset,
+				       void *from, unsigned int len) =
+	(void *) BPF_FUNC_lwt_seg6_store_bytes;
+static int (*bpf_lwt_seg6_action)(void *ctx, unsigned int action, void *param,
+				  unsigned int param_len) =
+	(void *) BPF_FUNC_lwt_seg6_action;
+static int (*bpf_lwt_seg6_adjust_srh)(void *ctx, unsigned int offset,
+				      unsigned int len) =
+	(void *) BPF_FUNC_lwt_seg6_adjust_srh;
 
 /* llvm builtin functions that eBPF C program may use to
  * emit BPF_LD_ABS and BPF_LD_IND instructions

tools/testing/selftests/bpf/test_lwt_seg6local.c new file +438 -0

438 lines not on this page · raw message

tools/testing/selftests/bpf/test_lwt_seg6local.sh new file +140 -0

140 lines not on this page · raw message

Signature · 1 line

2.16.1