[Qemu-devel] [PATCH] Add IP checksuming functions to qemu.

[Gerd Hoffmann <kraxel@redhat.com>]

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  Hi folks,

This patch adds IP checksumming functions to qemu, so not every nic
driver needs do to it on its own.

cheers,
  Gerd

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>From 1070650dcedeb966fd9baf499c1f85488a1aa48c Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 29 Jul 2008 13:25:12 +0200
Subject: [PATCH 04/22] Add IP checksumming functions to qemu.


Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 Makefile.target |    2 +-
 net-checksum.c  |   69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 net.h           |    7 +++++
 3 files changed, 77 insertions(+), 1 deletions(-)
 create mode 100644 net-checksum.c

diff --git a/Makefile.target b/Makefile.target
index ff105c1..42162c3 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -472,7 +472,7 @@ endif #CONFIG_DARWIN_USER
 # System emulator target
 ifndef CONFIG_USER_ONLY
 
-OBJS=vl.o osdep.o monitor.o pci.o loader.o isa_mmio.o machine.o
+OBJS=vl.o osdep.o monitor.o pci.o loader.o isa_mmio.o machine.o net-checksum.o
 ifdef CONFIG_WIN32
 OBJS+=block-raw-win32.o
 else
diff --git a/net-checksum.c b/net-checksum.c
new file mode 100644
index 0000000..2aefae2
--- /dev/null
+++ b/net-checksum.c
@@ -0,0 +1,69 @@
+#include "hw/hw.h"
+#include "net.h"
+
+#define PROTO_TCP  6
+#define PROTO_UDP 17
+
+uint32_t net_checksum_add(int len, uint8_t *buf)
+{
+    uint32_t sum = 0;
+    int i;
+
+    for (i = 0; i < len; i++) {
+	if (i & 1)
+	    sum += (uint32_t)buf[i];
+	else
+	    sum += (uint32_t)buf[i] << 8;
+    }
+    return sum;
+}
+
+uint16_t net_checksum_finish(uint32_t sum)
+{
+    while (sum>>16)
+	sum = (sum & 0xFFFF)+(sum >> 16);
+    return ~sum;
+}
+
+uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
+                             uint8_t *addrs, uint8_t *buf)
+{
+    uint32_t sum = 0;
+
+    sum += net_checksum_add(length, buf);         // payload
+    sum += net_checksum_add(8, addrs);            // src + dst address
+    sum += proto + length;                        // protocol & length
+    return net_checksum_finish(sum);
+}
+
+void net_checksum_calculate(uint8_t *data, int length)
+{
+    int hlen, plen, proto, csum_offset;
+    uint16_t csum;
+
+    if ((data[14] & 0xf0) != 0x40)
+	return; /* not IPv4 */
+    hlen  = (data[14] & 0x0f) * 4;
+    plen  = (data[16] << 8 | data[17]) - hlen;
+    proto = data[23];
+
+    switch (proto) {
+    case PROTO_TCP:
+	csum_offset = 16;
+	break;
+    case PROTO_UDP:
+	csum_offset = 6;
+	break;
+    default:
+	return;
+    }
+
+    if (plen < csum_offset+2)
+	return;
+
+    data[14+hlen+csum_offset]   = 0;
+    data[14+hlen+csum_offset+1] = 0;
+    csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen);
+    data[14+hlen+csum_offset]   = csum >> 8;
+    data[14+hlen+csum_offset+1] = csum & 0xff;
+}
diff --git a/net.h b/net.h
index d00910f..5212b48 100644
--- a/net.h
+++ b/net.h
@@ -48,4 +48,11 @@ struct NICInfo {
 extern int nb_nics;
 extern NICInfo nd_table[MAX_NICS];
 
+/* checksumming functions (net-checksum.c) */
+uint32_t net_checksum_add(int len, uint8_t *buf);
+uint16_t net_checksum_finish(uint32_t sum);
+uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
+                             uint8_t *addrs, uint8_t *buf);
+void net_checksum_calculate(uint8_t *data, int length);
+
 #endif
-- 
1.5.4.1