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diff --git a/util/proxy_protocol.h b/util/proxy_protocol.h
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+/*
+ * util/proxy_protocol.h - PROXY protocol
+ *
+ * Copyright (c) 2022, NLnet Labs. All rights reserved.
+ *
+ * This software is open source.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 
+ * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * 
+ * Redistributions in binary form must reproduce the above copyright notice,
+ * this list of conditions and the following disclaimer in the documentation
+ * and/or other materials provided with the distribution.
+ * 
+ * Neither the name of the NLNET LABS nor the names of its contributors may
+ * be used to endorse or promote products derived from this software without
+ * specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/**
+ * \file
+ *
+ * This file contains PROXY protocol structs and functions.
+ * Only v2 is supported. TLVs are not currently supported.
+ */
+#ifndef PROXY_PROTOCOL_H
+#define PROXY_PROTOCOL_H
+
+#include "sldns/sbuffer.h"
+
+/** PROXYv2 minimum header size */
+#define PP2_HEADER_SIZE 16
+
+/** PROXYv2 header signature */
+#define PP2_SIG "\x0D\x0A\x0D\x0A\x00\x0D\x0A\x51\x55\x49\x54\x0A"
+#define PP2_SIG_LEN 12
+
+/** PROXYv2 version */
+#define PP2_VERSION 0x2
+
+/**
+ * PROXYv2 command.
+ */
+enum pp2_command {
+	PP2_CMD_LOCAL = 0x0,
+	PP2_CMD_PROXY = 0x1
+};
+
+/**
+ * PROXYv2 address family.
+ */
+enum pp2_af {
+	PP2_AF_UNSPEC = 0x0,
+	PP2_AF_INET = 0x1,
+	PP2_AF_INET6 = 0x2,
+	PP2_AF_UNIX = 0x3
+};
+
+/**
+ * PROXYv2 protocol.
+ */
+enum pp2_protocol {
+	PP2_PROT_UNSPEC = 0x0,
+	PP2_PROT_STREAM = 0x1,
+	PP2_PROT_DGRAM = 0x2
+};
+
+/**
+ * PROXYv2 header.
+ */
+struct pp2_header {
+	uint8_t sig[PP2_SIG_LEN];
+	uint8_t ver_cmd;
+	uint8_t fam_prot;
+	uint16_t len;
+	union {
+		struct {  /* for TCP/UDP over IPv4, len = 12 */
+			uint32_t src_addr;
+			uint32_t dst_addr;
+			uint16_t src_port;
+			uint16_t dst_port;
+		} addr4;
+		struct {  /* for TCP/UDP over IPv6, len = 36 */
+			uint8_t  src_addr[16];
+			uint8_t  dst_addr[16];
+			uint16_t src_port;
+			uint16_t dst_port;
+		} addr6;
+		struct {  /* for AF_UNIX sockets, len = 216 */
+			uint8_t src_addr[108];
+			uint8_t dst_addr[108];
+		} addru;
+	} addr;
+};
+
+/**
+ * Write a PROXYv2 header at the current position of the buffer.
+ * @param buf: the buffer to write to.
+ * @param src: the source address.
+ * @param stream: if the protocol is stream or datagram.
+ * @return 1 on success, 0 on failure.
+ */
+int pp2_write_to_buf(struct sldns_buffer* buf, struct sockaddr_storage* src,
+	int stream);
+
+/**
+ * Read a PROXYv2 header from the current position of the buffer.
+ * It does initial validation and returns a pointer to the buffer position on
+ * success.
+ * @param buf: the buffer to read from.
+ * @return the pointer to the buffer position on success, NULL on error.
+ */
+struct pp2_header* pp2_read_header(struct sldns_buffer* buf);
+
+#endif /* PROXY_PROTOCOL_H */