net: Add a separate file for IP checksumming
Move the checksum code out into its own file so it can be used elsewhere.
Also use a new version which supports a length which is not a multiple of
2 and add a new function to add two checksums.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/net.h b/include/net.h
index 3da35fe..73ea88b 100644
--- a/include/net.h
+++ b/include/net.h
@@ -482,6 +482,36 @@
extern void net_set_udp_header(uchar *pkt, IPaddr_t dest, int dport,
int sport, int len);
+/**
+ * compute_ip_checksum() - Compute IP checksum
+ *
+ * @addr: Address to check (must be 16-bit aligned)
+ * @nbytes: Number of bytes to check (normally a multiple of 2)
+ * @return 16-bit IP checksum
+ */
+unsigned compute_ip_checksum(const void *addr, unsigned nbytes);
+
+/**
+ * add_ip_checksums() - add two IP checksums
+ *
+ * @offset: Offset of first sum (if odd we do a byte-swap)
+ * @sum: First checksum
+ * @new_sum: New checksum to add
+ * @return updated 16-bit IP checksum
+ */
+unsigned add_ip_checksums(unsigned offset, unsigned sum, unsigned new_sum);
+
+/**
+ * ip_checksum_ok() - check if a checksum is correct
+ *
+ * This works by making sure the checksum sums to 0
+ *
+ * @addr: Address to check (must be 16-bit aligned)
+ * @nbytes: Number of bytes to check (normally a multiple of 2)
+ * @return true if the checksum matches, false if not
+ */
+int ip_checksum_ok(const void *addr, unsigned nbytes);
+
/* Checksum */
extern int NetCksumOk(uchar *, int); /* Return true if cksum OK */
extern uint NetCksum(uchar *, int); /* Calculate the checksum */
diff --git a/net/Makefile b/net/Makefile
index 9425950..e9cc8ad 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -7,6 +7,7 @@
#ccflags-y += -DDEBUG
+obj-y += checksum.o
obj-$(CONFIG_CMD_NET) += arp.o
obj-$(CONFIG_CMD_NET) += bootp.o
obj-$(CONFIG_CMD_CDP) += cdp.o
diff --git a/net/checksum.c b/net/checksum.c
new file mode 100644
index 0000000..a8c9ff5
--- /dev/null
+++ b/net/checksum.c
@@ -0,0 +1,60 @@
+/*
+ * This file was originally taken from the FreeBSD project.
+ *
+ * Copyright (c) 2001 Charles Mott <cm@linktel.net>
+ * Copyright (c) 2008 coresystems GmbH
+ * All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <common.h>
+#include <net.h>
+
+unsigned compute_ip_checksum(const void *vptr, unsigned nbytes)
+{
+ int sum, oddbyte;
+ const unsigned short *ptr = vptr;
+
+ sum = 0;
+ while (nbytes > 1) {
+ sum += *ptr++;
+ nbytes -= 2;
+ }
+ if (nbytes == 1) {
+ oddbyte = 0;
+ ((u8 *)&oddbyte)[0] = *(u8 *)ptr;
+ ((u8 *)&oddbyte)[1] = 0;
+ sum += oddbyte;
+ }
+ sum = (sum >> 16) + (sum & 0xffff);
+ sum += (sum >> 16);
+ sum = ~sum & 0xffff;
+
+ return sum;
+}
+
+unsigned add_ip_checksums(unsigned offset, unsigned sum, unsigned new)
+{
+ unsigned long checksum;
+
+ sum = ~sum & 0xffff;
+ new = ~new & 0xffff;
+ if (offset & 1) {
+ /*
+ * byte-swap the sum if it came from an odd offset; since the
+ * computation is endian independant this works.
+ */
+ new = ((new >> 8) & 0xff) | ((new << 8) & 0xff00);
+ }
+ checksum = sum + new;
+ if (checksum > 0xffff)
+ checksum -= 0xffff;
+
+ return (~checksum) & 0xffff;
+}
+
+int ip_checksum_ok(const void *addr, unsigned nbytes)
+{
+ return !(compute_ip_checksum(addr, nbytes) & 0xfffe);
+}