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authorPatrik Flykt <patrik.flykt@linux.intel.com>2013-12-20 17:16:15 +0200
committerTom Gundersen <teg@jklm.no>2013-12-22 14:28:00 +0100
commit0c6a3c888abd720b5ab28162d1ba4eadffde5272 (patch)
tree9f3ecc81db7317b071caf74d6a9563abb5c88860 /src/libsystemd-dhcp
parent77e8d29dd2ecfa7f11c31c8d96021d323ab3fe3a (diff)
libsystemd-dhcp: Fix checksum computation for buffer with odd size
Fix off-by-one error and notice that summing may need more than one round for the result to be in the lower 16 bits.
Diffstat (limited to 'src/libsystemd-dhcp')
-rw-r--r--src/libsystemd-dhcp/dhcp-client.c7
-rw-r--r--src/libsystemd-dhcp/test-dhcp-client.c7
2 files changed, 10 insertions, 4 deletions
diff --git a/src/libsystemd-dhcp/dhcp-client.c b/src/libsystemd-dhcp/dhcp-client.c
index 7dc1546128..68a3b1a1b6 100644
--- a/src/libsystemd-dhcp/dhcp-client.c
+++ b/src/libsystemd-dhcp/dhcp-client.c
@@ -382,10 +382,13 @@ static uint16_t client_checksum(void *buf, int len)
if (len & 0x01) {
odd = buf;
- sum += odd[len];
+ sum += odd[len - 1];
}
- return ~((sum & 0xffff) + (sum >> 16));
+ while (sum >> 16)
+ sum = (sum & 0xffff) + (sum >> 16);
+
+ return ~sum;
}
static void client_append_ip_headers(DHCPPacket *packet, uint16_t len)
diff --git a/src/libsystemd-dhcp/test-dhcp-client.c b/src/libsystemd-dhcp/test-dhcp-client.c
index d398510745..7400cc6837 100644
--- a/src/libsystemd-dhcp/test-dhcp-client.c
+++ b/src/libsystemd-dhcp/test-dhcp-client.c
@@ -102,10 +102,13 @@ static uint16_t client_checksum(void *buf, int len)
if (len & 0x01) {
odd = buf;
- sum += odd[len];
+ sum += odd[len - 1];
}
- return ~((sum & 0xffff) + (sum >> 16));
+ while (sum >> 16)
+ sum = (sum & 0xffff) + (sum >> 16);
+
+ return ~sum;
}
static void test_checksum(void)