From 7920ab2b95a4c6d2756687b9dee635e036d96dbc Mon Sep 17 00:00:00 2001
From: Martine Lenders <m.lenders@fu-berlin.de>
Date: Wed, 11 Aug 2021 11:43:06 +0200
Subject: [PATCH] dns_msg: make parsing input buffer const

---
 sys/include/net/dns/msg.h           |  3 ++-
 sys/net/application_layer/dns/msg.c | 12 +++++++-----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/sys/include/net/dns/msg.h b/sys/include/net/dns/msg.h
index 9a0975f291..8faa54f4a1 100644
--- a/sys/include/net/dns/msg.h
+++ b/sys/include/net/dns/msg.h
@@ -109,7 +109,8 @@ size_t dns_msg_compose_query(void *dns_buf, const char *domain_name,
  * @return  -EBADMSG, when an address corresponding to @p family can not be found
  *          in @p buf.
  */
-int dns_msg_parse_reply(uint8_t *buf, size_t len, int family, void *addr_out);
+int dns_msg_parse_reply(const uint8_t *buf, size_t len, int family,
+                        void *addr_out);
 
 #ifdef __cplusplus
 }
diff --git a/sys/net/application_layer/dns/msg.c b/sys/net/application_layer/dns/msg.c
index 8e119d9f7c..ea9d0854d3 100644
--- a/sys/net/application_layer/dns/msg.c
+++ b/sys/net/application_layer/dns/msg.c
@@ -61,14 +61,15 @@ static unsigned _put_short(uint8_t *out, uint16_t val)
     return 2;
 }
 
-static unsigned _get_short(uint8_t *buf)
+static unsigned _get_short(const uint8_t *buf)
 {
     uint16_t _tmp;
     memcpy(&_tmp, buf, 2);
     return _tmp;
 }
 
-static ssize_t _skip_hostname(const uint8_t *buf, size_t len, uint8_t *bufpos)
+static ssize_t _skip_hostname(const uint8_t *buf, size_t len,
+                              const uint8_t *bufpos)
 {
     const uint8_t *buflim = buf + len;
     unsigned res = 0;
@@ -129,11 +130,12 @@ size_t dns_msg_compose_query(void *dns_buf, const char *domain_name,
     return bufpos - buf;
 }
 
-int dns_msg_parse_reply(uint8_t *buf, size_t len, int family, void *addr_out)
+int dns_msg_parse_reply(const uint8_t *buf, size_t len, int family,
+                        void *addr_out)
 {
     const uint8_t *buflim = buf + len;
-    dns_hdr_t *hdr = (dns_hdr_t *)buf;
-    uint8_t *bufpos = buf + sizeof(*hdr);
+    const dns_hdr_t *hdr = (dns_hdr_t *)buf;
+    const uint8_t *bufpos = buf + sizeof(*hdr);
 
     /* skip all queries that are part of the reply */
     for (unsigned n = 0; n < ntohs(hdr->qdcount); n++) {