[PATCH v3 13/19] psp: provide encapsulation helper for drivers

[Daniel Zahka <daniel.zahka@gmail.com>]

From: Raed Salem <raeds@nvidia.com>

Create a new function psp_encapsulate(), which takes a TCP packet and
PSP encapsulates it according to the "Transport Mode Packet Format"
section of the PSP Architecture Specification.

psp_encapsulate() does not push a PSP trailer onto the skb. Only IPv6
is supported. Virtualization cookie is not included.

Signed-off-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
---

Notes:
    v3:
    - patch introduced

 include/net/psp/functions.h |  2 ++
 include/net/psp/types.h     |  2 ++
 net/psp/psp_main.c          | 57 +++++++++++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+)

diff --git a/include/net/psp/functions.h b/include/net/psp/functions.h
index 1b414692504b..afb4f5929eec 100644
--- a/include/net/psp/functions.h
+++ b/include/net/psp/functions.h
@@ -16,6 +16,8 @@ struct psp_dev *
 psp_dev_create(struct net_device *netdev, struct psp_dev_ops *psd_ops,
 	       struct psp_dev_caps *psd_caps, void *priv_ptr);
 void psp_dev_unregister(struct psp_dev *psd);
+bool psp_encapsulate(struct net *net, struct sk_buff *skb,
+		     __be32 spi, u8 ver, __be16 sport);
 
 /* Kernel-facing API */
 void psp_assoc_put(struct psp_assoc *pas);
diff --git a/include/net/psp/types.h b/include/net/psp/types.h
index 383a1afab46d..fb8a31cbaae7 100644
--- a/include/net/psp/types.h
+++ b/include/net/psp/types.h
@@ -20,6 +20,8 @@ struct psphdr {
 	__be64	vc[]; /* optional */
 };
 
+#define PSP_ENCAP_HLEN (sizeof(struct udphdr) + sizeof(struct psphdr))
+
 #define PSP_SPI_KEY_ID		GENMASK(30, 0)
 #define PSP_SPI_KEY_PHASE	BIT(31)
 
diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
index 99facb158abb..8229a004ba6e 100644
--- a/net/psp/psp_main.c
+++ b/net/psp/psp_main.c
@@ -1,10 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
+#include <linux/bitfield.h>
 #include <linux/list.h>
 #include <linux/netdevice.h>
 #include <linux/xarray.h>
 #include <net/net_namespace.h>
 #include <net/psp.h>
+#include <net/udp.h>
 
 #include "psp.h"
 #include "psp-nl-gen.h"
@@ -138,6 +140,61 @@ void psp_dev_unregister(struct psp_dev *psd)
 }
 EXPORT_SYMBOL(psp_dev_unregister);
 
+static void psp_write_headers(struct net *net, struct sk_buff *skb,
+			      __be32 spi, u8 ver, unsigned int udp_len,
+			      __be16 sport)
+{
+	struct udphdr *uh = udp_hdr(skb);
+	struct psphdr *psph = (struct psphdr *)(uh + 1);
+
+	uh->dest = htons(PSP_DEFAULT_UDP_PORT);
+	uh->source = udp_flow_src_port(net, skb, 0, 0, false);
+	uh->check = 0;
+	uh->len = htons(udp_len);
+
+	psph->nexthdr = IPPROTO_TCP;
+	psph->hdrlen = PSP_HDRLEN_NOOPT;
+	psph->crypt_offset = 0;
+	psph->verfl = FIELD_PREP(PSPHDR_VERFL_VERSION, ver) |
+		      FIELD_PREP(PSPHDR_VERFL_ONE, 1);
+	psph->spi = spi;
+	memset(&psph->iv, 0, sizeof(psph->iv));
+}
+
+/* Encapsulate a TCP packet with PSP by adding the UDP+PSP headers and filling
+ * them in.
+ */
+bool psp_encapsulate(struct net *net, struct sk_buff *skb,
+		     __be32 spi, u8 ver, __be16 sport)
+{
+	u32 network_len = skb_network_header_len(skb);
+	u32 ethr_len = skb_mac_header_len(skb);
+	u32 bufflen = ethr_len + network_len;
+	struct ipv6hdr *ip6;
+
+	if (skb_cow_head(skb, PSP_ENCAP_HLEN))
+		return false;
+
+	skb_push(skb, PSP_ENCAP_HLEN);
+	skb->mac_header		-= PSP_ENCAP_HLEN;
+	skb->network_header	-= PSP_ENCAP_HLEN;
+	skb->transport_header	-= PSP_ENCAP_HLEN;
+	memmove(skb->data, skb->data + PSP_ENCAP_HLEN, bufflen);
+
+	ip6 = ipv6_hdr(skb);
+	skb_set_inner_ipproto(skb, IPPROTO_TCP);
+	ip6->nexthdr = IPPROTO_UDP;
+	be16_add_cpu(&ip6->payload_len, PSP_ENCAP_HLEN);
+
+	skb_set_inner_transport_header(skb, skb_transport_offset(skb) + PSP_ENCAP_HLEN);
+	skb->encapsulation = 1;
+	psp_write_headers(net, skb, spi, ver,
+			  skb->len - skb_transport_offset(skb), sport);
+
+	return true;
+}
+EXPORT_SYMBOL(psp_encapsulate);
+
 static int __init psp_init(void)
 {
 	mutex_init(&psp_devs_lock);
-- 
2.47.1