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2023-12-11 1f93a7dfd1f8d5ff7a5c53246c7534fe2332d6f4

 kernel/net/ipv6/fou6.c
..
..
@@ -1,9 +1,11 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 #include <linux/module.h>
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 #include <linux/errno.h>
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 #include <linux/socket.h>
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 #include <linux/skbuff.h>
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 #include <linux/ip.h>
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 #include <linux/udp.h>
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+#include <linux/icmpv6.h>
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 #include <linux/types.h>
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 #include <linux/kernel.h>
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 #include <net/fou.h>
..
..
@@ -69,14 +71,100 @@
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 	return 0;
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 }
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73
 
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+static int gue6_err_proto_handler(int proto, struct sk_buff *skb,
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+				  struct inet6_skb_parm *opt,
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+				  u8 type, u8 code, int offset, __be32 info)
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+{
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+	const struct inet6_protocol *ipprot;
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+
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+	ipprot = rcu_dereference(inet6_protos[proto]);
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+	if (ipprot && ipprot->err_handler) {
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+		if (!ipprot->err_handler(skb, opt, type, code, offset, info))
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+			return 0;
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+	}
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+
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+	return -ENOENT;
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+}
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+
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+static int gue6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
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+		    u8 type, u8 code, int offset, __be32 info)
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+{
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+	int transport_offset = skb_transport_offset(skb);
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+	struct guehdr *guehdr;
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+	size_t len, optlen;
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+	int ret;
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+
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+	len = sizeof(struct udphdr) + sizeof(struct guehdr);
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+	if (!pskb_may_pull(skb, transport_offset + len))
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+		return -EINVAL;
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+
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+	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
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+
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+	switch (guehdr->version) {
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+	case 0: /* Full GUE header present */
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+		break;
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+	case 1: {
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+		/* Direct encasulation of IPv4 or IPv6 */
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+		skb_set_transport_header(skb, -(int)sizeof(struct icmp6hdr));
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+
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+		switch (((struct iphdr *)guehdr)->version) {
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+		case 4:
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+			ret = gue6_err_proto_handler(IPPROTO_IPIP, skb, opt,
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+						     type, code, offset, info);
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+			goto out;
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+		case 6:
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+			ret = gue6_err_proto_handler(IPPROTO_IPV6, skb, opt,
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+						     type, code, offset, info);
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+			goto out;
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+		default:
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+			ret = -EOPNOTSUPP;
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+			goto out;
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+		}
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+	}
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+	default: /* Undefined version */
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+		return -EOPNOTSUPP;
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+	}
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+
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+	if (guehdr->control)
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+		return -ENOENT;
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+
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+	optlen = guehdr->hlen << 2;
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+
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+	if (!pskb_may_pull(skb, transport_offset + len + optlen))
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+		return -EINVAL;
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+
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+	guehdr = (struct guehdr *)&udp_hdr(skb)[1];
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+	if (validate_gue_flags(guehdr, optlen))
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+		return -EINVAL;
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+
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+	/* Handling exceptions for direct UDP encapsulation in GUE would lead to
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+	 * recursion. Besides, this kind of encapsulation can't even be
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+	 * configured currently. Discard this.
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+	 */
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+	if (guehdr->proto_ctype == IPPROTO_UDP ||
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+	    guehdr->proto_ctype == IPPROTO_UDPLITE)
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+		return -EOPNOTSUPP;
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+
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+	skb_set_transport_header(skb, -(int)sizeof(struct icmp6hdr));
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+	ret = gue6_err_proto_handler(guehdr->proto_ctype, skb,
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+				     opt, type, code, offset, info);
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+
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+out:
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+	skb_set_transport_header(skb, transport_offset);
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+	return ret;
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+}
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+
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+
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 static const struct ip6_tnl_encap_ops fou_ip6tun_ops = {
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 	.encap_hlen = fou_encap_hlen,
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 	.build_header = fou6_build_header,
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+	.err_handler = gue6_err,
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 };
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163
 
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 static const struct ip6_tnl_encap_ops gue_ip6tun_ops = {
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 	.encap_hlen = gue_encap_hlen,
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 	.build_header = gue6_build_header,
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+	.err_handler = gue6_err,
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 };
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169
 
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 static int ip6_tnl_encap_add_fou_ops(void)
..
..
@@ -136,3 +224,4 @@
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 module_exit(fou6_fini);
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 MODULE_AUTHOR("Tom Herbert <therbert@google.com>");
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 MODULE_LICENSE("GPL");
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+MODULE_DESCRIPTION("Foo over UDP (IPv6)");