net: ptp: move PTP classifier in its own file

This commit fixes a build error reported by Fengguang, that is
triggered when CONFIG_NETWORK_PHY_TIMESTAMPING is not set:

  ERROR: "ptp_classify_raw" [drivers/net/ethernet/oki-semi/pch_gbe/pch_gbe.ko] undefined!

The fix is to introduce its own file for the PTP BPF classifier,
so that PTP_1588_CLOCK and/or NETWORK_PHY_TIMESTAMPING can select
it independently from each other. IXP4xx driver on ARM needs to
select it as well since it does not seem to select PTP_1588_CLOCK
or similar that would pull it in automatically.

This also allows for hiding all of the internals of the BPF PTP
program inside that file, and only exporting relevant API bits
to drivers.

This patch also adds a kdoc documentation of ptp_classify_raw()
API to make it clear that it can return PTP_CLASS_* defines. Also,
the BPF program has been translated into bpf_asm code, so that it
can be more easily read and altered (extensively documented in [1]).

In the kernel tree under tools/net/ we have bpf_asm and bpf_dbg
tools, so the commented program can simply be translated via
`./bpf_asm -c prog` where prog is a file that contains the
commented code. This makes it easily readable/verifiable and when
there's a need to change something, jump offsets etc do not need
to be replaced manually which can be very error prone. Instead,
a newly translated version via bpf_asm can simply replace the old
code. I have checked opcode diffs before/after and it's the very
same filter.

  [1] Documentation/networking/filter.txt

Fixes: 164d8c666521 ("net: ptp: do not reimplement PTP/BPF classifier")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Jiri Benc <jbenc@redhat.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 142 insertions, 18 deletions

diff --git a/net/core/Makefile b/net/core/Makefile
index 9628c20acff6..826b925aa453 100644
--- a/net/core/Makefile
+++ b/net/core/Makefile
@@ -21,5 +21,6 @@ obj-$(CONFIG_FIB_RULES) += fib_rules.o
 obj-$(CONFIG_TRACEPOINTS) += net-traces.o
 obj-$(CONFIG_NET_DROP_MONITOR) += drop_monitor.o
 obj-$(CONFIG_NETWORK_PHY_TIMESTAMPING) += timestamping.o
+obj-$(CONFIG_NET_PTP_CLASSIFY) += ptp_classifier.o
 obj-$(CONFIG_CGROUP_NET_PRIO) += netprio_cgroup.o
 obj-$(CONFIG_CGROUP_NET_CLASSID) += netclassid_cgroup.o
diff --git a/net/core/ptp_classifier.c b/net/core/ptp_classifier.c
new file mode 100644
index 000000000000..eaba0f68f860
--- /dev/null
+++ b/net/core/ptp_classifier.c
@@ -0,0 +1,141 @@
+/* PTP classifier
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+/* The below program is the bpf_asm (tools/net/) representation of
+ * the opcode array in the ptp_filter structure.
+ *
+ * For convenience, this can easily be altered and reviewed with
+ * bpf_asm and bpf_dbg, e.g. `./bpf_asm -c prog` where prog is a
+ * simple file containing the below program:
+ *
+ * ldh [12]                        ; load ethertype
+ *
+ * ; PTP over UDP over IPv4 over Ethernet
+ * test_ipv4:
+ *   jneq #0x800, test_ipv6        ; ETH_P_IP ?
+ *   ldb [23]                      ; load proto
+ *   jneq #17, drop_ipv4           ; IPPROTO_UDP ?
+ *   ldh [20]                      ; load frag offset field
+ *   jset #0x1fff, drop_ipv4       ; don't allow fragments
+ *   ldxb 4*([14]&0xf)             ; load IP header len
+ *   ldh [x + 16]                  ; load UDP dst port
+ *   jneq #319, drop_ipv4          ; is port PTP_EV_PORT ?
+ *   ldh [x + 22]                  ; load payload
+ *   and #0xf                      ; mask PTP_CLASS_VMASK
+ *   or #0x10                      ; PTP_CLASS_IPV4
+ *   ret a                         ; return PTP class
+ *   drop_ipv4: ret #0x0           ; PTP_CLASS_NONE
+ *
+ * ; PTP over UDP over IPv6 over Ethernet
+ * test_ipv6:
+ *   jneq #0x86dd, test_8021q      ; ETH_P_IPV6 ?
+ *   ldb [20]                      ; load proto
+ *   jneq #17, drop_ipv6           ; IPPROTO_UDP ?
+ *   ldh [56]                      ; load UDP dst port
+ *   jneq #319, drop_ipv6          ; is port PTP_EV_PORT ?
+ *   ldh [62]                      ; load payload
+ *   and #0xf                      ; mask PTP_CLASS_VMASK
+ *   or #0x20                      ; PTP_CLASS_IPV6
+ *   ret a                         ; return PTP class
+ *   drop_ipv6: ret #0x0           ; PTP_CLASS_NONE
+ *
+ * ; PTP over 802.1Q over Ethernet
+ * test_8021q:
+ *   jneq #0x8100, test_ieee1588   ; ETH_P_8021Q ?
+ *   ldh [16]                      ; load inner type
+ *   jneq #0x88f7, drop_ieee1588   ; ETH_P_1588 ?
+ *   ldb [18]                      ; load payload
+ *   and #0x8                      ; as we don't have ports here, test
+ *   jneq #0x0, drop_ieee1588      ; for PTP_GEN_BIT and drop these
+ *   ldh [18]                      ; reload payload
+ *   and #0xf                      ; mask PTP_CLASS_VMASK
+ *   or #0x40                      ; PTP_CLASS_V2_VLAN
+ *   ret a                         ; return PTP class
+ *
+ * ; PTP over Ethernet
+ * test_ieee1588:
+ *   jneq #0x88f7, drop_ieee1588   ; ETH_P_1588 ?
+ *   ldb [14]                      ; load payload
+ *   and #0x8                      ; as we don't have ports here, test
+ *   jneq #0x0, drop_ieee1588      ; for PTP_GEN_BIT and drop these
+ *   ldh [14]                      ; reload payload
+ *   and #0xf                      ; mask PTP_CLASS_VMASK
+ *   or #0x30                      ; PTP_CLASS_L2
+ *   ret a                         ; return PTP class
+ *   drop_ieee1588: ret #0x0       ; PTP_CLASS_NONE
+ */
+
+#include <linux/skbuff.h>
+#include <linux/filter.h>
+#include <linux/ptp_classify.h>
+
+static struct sk_filter *ptp_insns __read_mostly;
+
+unsigned int ptp_classify_raw(const struct sk_buff *skb)
+{
+	return SK_RUN_FILTER(ptp_insns, skb);
+}
+EXPORT_SYMBOL_GPL(ptp_classify_raw);
+
+void __init ptp_classifier_init(void)
+{
+	static struct sock_filter ptp_filter[] = {
+		{ 0x28,  0,  0, 0x0000000c },
+		{ 0x15,  0, 12, 0x00000800 },
+		{ 0x30,  0,  0, 0x00000017 },
+		{ 0x15,  0,  9, 0x00000011 },
+		{ 0x28,  0,  0, 0x00000014 },
+		{ 0x45,  7,  0, 0x00001fff },
+		{ 0xb1,  0,  0, 0x0000000e },
+		{ 0x48,  0,  0, 0x00000010 },
+		{ 0x15,  0,  4, 0x0000013f },
+		{ 0x48,  0,  0, 0x00000016 },
+		{ 0x54,  0,  0, 0x0000000f },
+		{ 0x44,  0,  0, 0x00000010 },
+		{ 0x16,  0,  0, 0x00000000 },
+		{ 0x06,  0,  0, 0x00000000 },
+		{ 0x15,  0,  9, 0x000086dd },
+		{ 0x30,  0,  0, 0x00000014 },
+		{ 0x15,  0,  6, 0x00000011 },
+		{ 0x28,  0,  0, 0x00000038 },
+		{ 0x15,  0,  4, 0x0000013f },
+		{ 0x28,  0,  0, 0x0000003e },
+		{ 0x54,  0,  0, 0x0000000f },
+		{ 0x44,  0,  0, 0x00000020 },
+		{ 0x16,  0,  0, 0x00000000 },
+		{ 0x06,  0,  0, 0x00000000 },
+		{ 0x15,  0,  9, 0x00008100 },
+		{ 0x28,  0,  0, 0x00000010 },
+		{ 0x15,  0, 15, 0x000088f7 },
+		{ 0x30,  0,  0, 0x00000012 },
+		{ 0x54,  0,  0, 0x00000008 },
+		{ 0x15,  0, 12, 0x00000000 },
+		{ 0x28,  0,  0, 0x00000012 },
+		{ 0x54,  0,  0, 0x0000000f },
+		{ 0x44,  0,  0, 0x00000040 },
+		{ 0x16,  0,  0, 0x00000000 },
+		{ 0x15,  0,  7, 0x000088f7 },
+		{ 0x30,  0,  0, 0x0000000e },
+		{ 0x54,  0,  0, 0x00000008 },
+		{ 0x15,  0,  4, 0x00000000 },
+		{ 0x28,  0,  0, 0x0000000e },
+		{ 0x54,  0,  0, 0x0000000f },
+		{ 0x44,  0,  0, 0x00000030 },
+		{ 0x16,  0,  0, 0x00000000 },
+		{ 0x06,  0,  0, 0x00000000 },
+	};
+	struct sock_fprog ptp_prog = {
+		.len = ARRAY_SIZE(ptp_filter), .filter = ptp_filter,
+	};
+
+	BUG_ON(sk_unattached_filter_create(&ptp_insns, &ptp_prog));
+}
diff --git a/net/core/timestamping.c b/net/core/timestamping.c
index 9ff26b3cc021..6521dfd8b7c8 100644
--- a/net/core/timestamping.c
+++ b/net/core/timestamping.c
@@ -23,14 +23,6 @@
 #include <linux/skbuff.h>
 #include <linux/export.h>
 
-static struct sk_filter *ptp_insns __read_mostly;
-
-unsigned int ptp_classify_raw(const struct sk_buff *skb)
-{
-	return SK_RUN_FILTER(ptp_insns, skb);
-}
-EXPORT_SYMBOL_GPL(ptp_classify_raw);
-
 static unsigned int classify(const struct sk_buff *skb)
 {
 	if (likely(skb->dev && skb->dev->phydev &&
@@ -140,13 +132,3 @@ bool skb_defer_rx_timestamp(struct sk_buff *skb)
 	return false;
 }
 EXPORT_SYMBOL_GPL(skb_defer_rx_timestamp);
-
-void __init skb_timestamping_init(void)
-{
-	static struct sock_filter ptp_filter[] = { PTP_FILTER };
-	struct sock_fprog ptp_prog = {
-		.len = ARRAY_SIZE(ptp_filter), .filter = ptp_filter,
-	};
-
-	BUG_ON(sk_unattached_filter_create(&ptp_insns, &ptp_prog));
-}