From 4abab5ad6c8465a7528ccdd5f49367da05f78bbd Mon Sep 17 00:00:00 2001
From: Vladimir Azarov <avm@intermediate-node.net>
Date: Tue, 1 Oct 2024 15:47:05 +0200
Subject: Initial version

---
 src/network/dn_expand.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)
 create mode 100644 src/network/dn_expand.c

(limited to 'src/network/dn_expand.c')

diff --git a/src/network/dn_expand.c b/src/network/dn_expand.c
new file mode 100644
index 0000000..eac343a
--- /dev/null
+++ b/src/network/dn_expand.c
@@ -0,0 +1,33 @@
+#include <resolv.h>
+
+int __dn_expand(const unsigned char *base, const unsigned char *end, const unsigned char *src, char *dest, int space)
+{
+	const unsigned char *p = src;
+	char *dend, *dbegin = dest;
+	int len = -1, i, j;
+	if (p==end || space <= 0) return -1;
+	dend = dest + (space > 254 ? 254 : space);
+	/* detect reference loop using an iteration counter */
+	for (i=0; i < end-base; i+=2) {
+		/* loop invariants: p<end, dest<dend */
+		if (*p & 0xc0) {
+			if (p+1==end) return -1;
+			j = ((p[0] & 0x3f) << 8) | p[1];
+			if (len < 0) len = p+2-src;
+			if (j >= end-base) return -1;
+			p = base+j;
+		} else if (*p) {
+			if (dest != dbegin) *dest++ = '.';
+			j = *p++;
+			if (j >= end-p || j >= dend-dest) return -1;
+			while (j--) *dest++ = *p++;
+		} else {
+			*dest = 0;
+			if (len < 0) len = p+1-src;
+			return len;
+		}
+	}
+	return -1;
+}
+
+weak_alias(__dn_expand, dn_expand);
-- 
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