From e35d6a4fde9a0671bc7d2527ff6b55b0ce1b4b1e Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Sun, 21 Aug 2022 22:33:09 +0200
Subject: user: rename ethdump to netstack

---
 src/user/app/netstack/util.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 src/user/app/netstack/util.c

(limited to 'src/user/app/netstack/util.c')

diff --git a/src/user/app/netstack/util.c b/src/user/app/netstack/util.c
new file mode 100644
index 0000000..7c484f3
--- /dev/null
+++ b/src/user/app/netstack/util.c
@@ -0,0 +1,31 @@
+#include "util.h"
+
+/* https://www.w3.org/TR/PNG/#D-CRCAppendix */
+static uint32_t crc_table[256];
+uint32_t crc32(const uint8_t *buf, size_t len) {
+	if (!crc_table[1]) {
+		for (int i = 0; i < 256; i++) {
+			uint32_t c = i;
+			for (int j = 0; j < 8; j++)
+				c = ((c&1) ? 0xedb88320 : 0) ^ (c >> 1);
+			crc_table[i] = c;
+		}
+	}
+
+	uint32_t c = 0xFFFFFFFF;
+	for (size_t i = 0; i < len; i++)
+		c = crc_table[(c ^ buf[i]) & 0xff] ^ (c >> 8);
+	return ~c;
+}
+
+uint16_t ip_checksum(const uint8_t *buf, size_t len) {
+	uint32_t c = 0;
+	while (len >= 2) {
+		c += nget16(buf);
+		buf += 2; len -= 2;
+	}
+	if (len) c += (*buf) << 8;
+	while (c >= 0xFFFF)
+		c = (c & 0xFFFF) + (c >> 16);
+	return ~c;
+}
-- 
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