rps: Inspect PPTP encapsulated by GRE to get flow hash

The PPTP is encapsulated by GRE header with that GRE_VERSION bits
must contain one. But current GRE RPS needs the GRE_VERSION must be
zero. So RPS does not work for PPTP traffic.

In my test environment, there are four MIPS cores, and all traffic
are passed through by PPTP. As a result, only one core is 100% busy
while other three cores are very idle. After this patch, the usage
of four cores are balanced well.

Signed-off-by: Gao Feng <[email protected]>
Reviewed-by: Philip Prindeville <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: gfreewind

drivers/net/ppp/pptp.c

@@ -37,6 +37,7 @@
 #include <net/icmp.h>
 #include <net/route.h>
 #include <net/gre.h>
+#include <net/pptp.h>
 
 #include <linux/uaccess.h>
 
@@ -53,41 +54,6 @@ static struct proto pptp_sk_proto __read_mostly;
 static const struct ppp_channel_ops pptp_chan_ops;
 static const struct proto_ops pptp_ops;
 
-#define PPP_LCP_ECHOREQ 0x09
-#define PPP_LCP_ECHOREP 0x0A
-#define SC_RCV_BITS	(SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
-
-#define MISSING_WINDOW 20
-#define WRAPPED(curseq, lastseq)\
-	((((curseq) & 0xffffff00) == 0) &&\
-	(((lastseq) & 0xffffff00) == 0xffffff00))
-
-#define PPTP_GRE_PROTO  0x880B
-#define PPTP_GRE_VER    0x1
-
-#define PPTP_GRE_FLAG_C	0x80
-#define PPTP_GRE_FLAG_R	0x40
-#define PPTP_GRE_FLAG_K	0x20
-#define PPTP_GRE_FLAG_S	0x10
-#define PPTP_GRE_FLAG_A	0x80
-
-#define PPTP_GRE_IS_C(f) ((f)&PPTP_GRE_FLAG_C)
-#define PPTP_GRE_IS_R(f) ((f)&PPTP_GRE_FLAG_R)
-#define PPTP_GRE_IS_K(f) ((f)&PPTP_GRE_FLAG_K)
-#define PPTP_GRE_IS_S(f) ((f)&PPTP_GRE_FLAG_S)
-#define PPTP_GRE_IS_A(f) ((f)&PPTP_GRE_FLAG_A)
-
-#define PPTP_HEADER_OVERHEAD (2+sizeof(struct pptp_gre_header))
-struct pptp_gre_header {
-	u8  flags;
-	u8  ver;
-	__be16 protocol;
-	__be16 payload_len;
-	__be16 call_id;
-	__be32 seq;
-	__be32 ack;
-} __packed;
-
 static struct pppox_sock *lookup_chan(u16 call_id, __be32 s_addr)
 {
 	struct pppox_sock *sock;

include/net/gre.h

@@ -7,7 +7,15 @@
 struct gre_base_hdr {
 	__be16 flags;
 	__be16 protocol;
-};
+} __packed;
+
+struct gre_full_hdr {
+	struct gre_base_hdr fixed_header;
+	__be16 csum;
+	__be16 reserved1;
+	__be32 key;
+	__be32 seq;
+} __packed;
 #define GRE_HEADER_SECTION 4
 
 #define GREPROTO_CISCO		0

include/net/pptp.h

@@ -0,0 +1,40 @@
+#ifndef _NET_PPTP_H
+#define _NET_PPTP_H
+
+#define PPP_LCP_ECHOREQ 0x09
+#define PPP_LCP_ECHOREP 0x0A
+#define SC_RCV_BITS     (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)
+
+#define MISSING_WINDOW 20
+#define WRAPPED(curseq, lastseq)\
+	((((curseq) & 0xffffff00) == 0) &&\
+	(((lastseq) & 0xffffff00) == 0xffffff00))
+
+#define PPTP_GRE_PROTO  0x880B
+#define PPTP_GRE_VER    0x1
+
+#define PPTP_GRE_FLAG_C 0x80
+#define PPTP_GRE_FLAG_R 0x40
+#define PPTP_GRE_FLAG_K 0x20
+#define PPTP_GRE_FLAG_S 0x10
+#define PPTP_GRE_FLAG_A 0x80
+
+#define PPTP_GRE_IS_C(f) ((f)&PPTP_GRE_FLAG_C)
+#define PPTP_GRE_IS_R(f) ((f)&PPTP_GRE_FLAG_R)
+#define PPTP_GRE_IS_K(f) ((f)&PPTP_GRE_FLAG_K)
+#define PPTP_GRE_IS_S(f) ((f)&PPTP_GRE_FLAG_S)
+#define PPTP_GRE_IS_A(f) ((f)&PPTP_GRE_FLAG_A)
+
+#define PPTP_HEADER_OVERHEAD (2+sizeof(struct pptp_gre_header))
+struct pptp_gre_header {
+	u8  flags;
+	u8  ver;
+	__be16 protocol;
+	__be16 payload_len;
+	__be16 call_id;
+	__be32 seq;
+	__be32 ack;
+} __packed;
+
+
+#endif

include/uapi/linux/if_tunnel.h

@@ -24,9 +24,14 @@
 #define GRE_SEQ		__cpu_to_be16(0x1000)
 #define GRE_STRICT	__cpu_to_be16(0x0800)
 #define GRE_REC		__cpu_to_be16(0x0700)
-#define GRE_FLAGS	__cpu_to_be16(0x00F8)
+#define GRE_ACK		__cpu_to_be16(0x0080)
+#define GRE_FLAGS	__cpu_to_be16(0x0078)
 #define GRE_VERSION	__cpu_to_be16(0x0007)
 
+#define GRE_VERSION_1	__cpu_to_be16(0x0001)
+#define GRE_PROTO_PPP	__cpu_to_be16(0x880b)
+#define GRE_PPTP_KEY_MASK	__cpu_to_be32(0xffff)
+
 struct ip_tunnel_parm {
 	char			name[IFNAMSIZ];
 	int			link;

net/core/flow_dissector.c

@@ -6,6 +6,8 @@
 #include <linux/if_vlan.h>
 #include <net/ip.h>
 #include <net/ipv6.h>
+#include <net/gre.h>
+#include <net/pptp.h>
 #include <linux/igmp.h>
 #include <linux/icmp.h>
 #include <linux/sctp.h>
@@ -338,32 +340,42 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 ip_proto_again:
 	switch (ip_proto) {
 	case IPPROTO_GRE: {
-		struct gre_hdr {
-			__be16 flags;
-			__be16 proto;
-		} *hdr, _hdr;
+		struct gre_base_hdr *hdr, _hdr;
+		u16 gre_ver;
+		int offset = 0;
 
 		hdr = __skb_header_pointer(skb, nhoff, sizeof(_hdr), data, hlen, &_hdr);
 		if (!hdr)
 			goto out_bad;
-		/*
-		 * Only look inside GRE if version zero and no
-		 * routing
-		 */
-		if (hdr->flags & (GRE_VERSION | GRE_ROUTING))
+
+		/* Only look inside GRE without routing */
+		if (hdr->flags & GRE_ROUTING)
 			break;
 
-		proto = hdr->proto;
-		nhoff += 4;
+		/* Only look inside GRE for version 0 and 1 */
+		gre_ver = ntohs(hdr->flags & GRE_VERSION);
+		if (gre_ver > 1)
+			break;
+
+		proto = hdr->protocol;
+		if (gre_ver) {
+			/* Version1 must be PPTP, and check the flags */
+			if (!(proto == GRE_PROTO_PPP && (hdr->flags & GRE_KEY)))
+				break;
+		}
+
+		offset += sizeof(struct gre_base_hdr);
+
 		if (hdr->flags & GRE_CSUM)
-			nhoff += 4;
+			offset += sizeof(((struct gre_full_hdr *)0)->csum) +
+				  sizeof(((struct gre_full_hdr *)0)->reserved1);
+
 		if (hdr->flags & GRE_KEY) {
 			const __be32 *keyid;
 			__be32 _keyid;
 
-			keyid = __skb_header_pointer(skb, nhoff, sizeof(_keyid),
+			keyid = __skb_header_pointer(skb, nhoff + offset, sizeof(_keyid),
 						     data, hlen, &_keyid);
-
 			if (!keyid)
 				goto out_bad;
 
@@ -372,32 +384,65 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 				key_keyid = skb_flow_dissector_target(flow_dissector,
 								      FLOW_DISSECTOR_KEY_GRE_KEYID,
 								      target_container);
-				key_keyid->keyid = *keyid;
+				if (gre_ver == 0)
+					key_keyid->keyid = *keyid;
+				else
+					key_keyid->keyid = *keyid & GRE_PPTP_KEY_MASK;
 			}
-			nhoff += 4;
+			offset += sizeof(((struct gre_full_hdr *)0)->key);
 		}
+
 		if (hdr->flags & GRE_SEQ)
-			nhoff += 4;
-		if (proto == htons(ETH_P_TEB)) {
-			const struct ethhdr *eth;
-			struct ethhdr _eth;
-
-			eth = __skb_header_pointer(skb, nhoff,
-						   sizeof(_eth),
-						   data, hlen, &_eth);
-			if (!eth)
+			offset += sizeof(((struct pptp_gre_header *)0)->seq);
+
+		if (gre_ver == 0) {
+			if (proto == htons(ETH_P_TEB)) {
+				const struct ethhdr *eth;
+				struct ethhdr _eth;
+
+				eth = __skb_header_pointer(skb, nhoff + offset,
+							   sizeof(_eth),
+							   data, hlen, &_eth);
+				if (!eth)
+					goto out_bad;
+				proto = eth->h_proto;
+				offset += sizeof(*eth);
+
+				/* Cap headers that we access via pointers at the
+				 * end of the Ethernet header as our maximum alignment
+				 * at that point is only 2 bytes.
+				 */
+				if (NET_IP_ALIGN)
+					hlen = (nhoff + offset);
+			}
+		} else { /* version 1, must be PPTP */
+			u8 _ppp_hdr[PPP_HDRLEN];
+			u8 *ppp_hdr;
+
+			if (hdr->flags & GRE_ACK)
+				offset += sizeof(((struct pptp_gre_header *)0)->ack);
+
+			ppp_hdr = skb_header_pointer(skb, nhoff + offset,
+						     sizeof(_ppp_hdr), _ppp_hdr);
+			if (!ppp_hdr)
 				goto out_bad;
-			proto = eth->h_proto;
-			nhoff += sizeof(*eth);
-
-			/* Cap headers that we access via pointers at the
-			 * end of the Ethernet header as our maximum alignment
-			 * at that point is only 2 bytes.
-			 */
-			if (NET_IP_ALIGN)
-				hlen = nhoff;
+
+			switch (PPP_PROTOCOL(ppp_hdr)) {
+			case PPP_IP:
+				proto = htons(ETH_P_IP);
+				break;
+			case PPP_IPV6:
+				proto = htons(ETH_P_IPV6);
+				break;
+			default:
+				/* Could probably catch some more like MPLS */
+				break;
+			}
+
+			offset += PPP_HDRLEN;
 		}
 
+		nhoff += offset;
 		key_control->flags |= FLOW_DIS_ENCAPSULATION;
 		if (flags & FLOW_DISSECTOR_F_STOP_AT_ENCAP)
 			goto out_good;