Changeset 1cc8b42 in mainline for uspace/srv/inet/pdu.c

Timestamp:

2012-02-27T20:34:58Z (12 years ago)

Author:

Jiri Svoboda <jiri@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

f9d3dd4

Parents:

56792a2

Message:

Correct IP checksum and identification.

File:

• uspace/srv/inet/pdu.c (modified) (5 diffs)

uspace/srv/inet/pdu.c

@@ -39 +39 @@
 #include <byteorder.h>
 #include <errno.h>
+#include <fibril_synch.h>
 #include <io/log.h>
 #include <mem.h>
@@ -46 +47 @@
 #include "inet_std.h"
 #include "pdu.h"
+
+static FIBRIL_MUTEX_INITIALIZE(ip_ident_lock);
+static uint16_t ip_ident = 0;
+
+#define INET_CHECKSUM_INIT 0xffff
+
+/** One's complement addition.
+ *
+ * Result is a + b + carry.
+ */
+static uint16_t inet_ocadd16(uint16_t a, uint16_t b)
+{
+        uint32_t s;
+
+        s = (uint32_t)a + (uint32_t)b;
+        return (s & 0xffff) + (s >> 16);
+}
+
+static uint16_t inet_checksum_calc(uint16_t ivalue, void *data, size_t size)
+{
+        uint16_t sum;
+        uint16_t w;
+        size_t words, i;
+        uint8_t *bdata;
+
+        sum = ~ivalue;
+        words = size / 2;
+        bdata = (uint8_t *)data;
+
+        for (i = 0; i < words; i++) {
+                w = ((uint16_t)bdata[2*i] << 8) | bdata[2*i + 1];
+                sum = inet_ocadd16(sum, w);
+        }
+
+        if (size % 2 != 0) {
+                w = ((uint16_t)bdata[2*words] << 8);
+                sum = inet_ocadd16(sum, w);
+        }
+
+        return ~sum;
+}
 
 /** Encode Internet PDU.
@@ -56 +98 @@
         size_t hdr_size;
         size_t data_offs;
+        uint16_t chksum;
+        uint16_t ident;
+
+        fibril_mutex_lock(&ip_ident_lock);
+        ident = ++ip_ident;
+        fibril_mutex_unlock(&ip_ident_lock);
 
         hdr_size = sizeof(ip_header_t);
@@ -69 +117 @@
         hdr->tos = packet->tos;
         hdr->tot_len = host2uint16_t_be(size);
-        hdr->id = host2uint16_t_be(42);
+        hdr->id = host2uint16_t_be(ident);
         hdr->flags_foff = host2uint16_t_be(packet->df ?
             BIT_V(uint16_t, FF_FLAG_DF) : 0);
@@ -78 +126 @@
         hdr->dest_addr = host2uint32_t_be(packet->dest.ipv4);
 
+        chksum = inet_checksum_calc(INET_CHECKSUM_INIT, (void *)hdr, hdr_size);
+        hdr->chksum = host2uint16_t_be(chksum);
+
         memcpy((uint8_t *)data + data_offs, packet->data, packet->size);