diff mbox

[1/4] net: move CRC32 calculation from compute_mcast_idx() into its own net_crc32() function

Message ID 1503065708-28277-2-git-send-email-mark.cave-ayland@ilande.co.uk
State New
Headers show

Commit Message

Mark Cave-Ayland Aug. 18, 2017, 2:15 p.m. UTC 
Separate out the standard ethernet CRC32 calculation into a new net_crc32()
function, renaming the constant POLYNOMIAL to POLYNOMIAL_BE to make it clear
that this is a big-endian CRC32 calculation.

Then remove the existing implementation from compute_mcast_idx() and call the
new function in its place.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 include/net/net.h |    3 ++-
 net/net.c         |   16 +++++++++++-----
 2 files changed, 13 insertions(+), 6 deletions(-)

Comments

Philippe Mathieu-Daudé Aug. 18, 2017, 4:51 p.m. UTC | #1 
On 08/18/2017 11:15 AM, Mark Cave-Ayland wrote:
> Separate out the standard ethernet CRC32 calculation into a new net_crc32()
> function, renaming the constant POLYNOMIAL to POLYNOMIAL_BE to make it clear
> that this is a big-endian CRC32 calculation.
> 
> Then remove the existing implementation from compute_mcast_idx() and call the
> new function in its place.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>   include/net/net.h |    3 ++-
>   net/net.c         |   16 +++++++++++-----
>   2 files changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/include/net/net.h b/include/net/net.h
> index 1c55a93..586098c 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -227,7 +227,8 @@ NetClientState *net_hub_port_find(int hub_id);
>   
>   void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd);
>   
> -#define POLYNOMIAL 0x04c11db6
> +#define POLYNOMIAL_BE 0x04c11db6
> +uint32_t net_crc32(const uint8_t *p, int len);
>   unsigned compute_mcast_idx(const uint8_t *ep);
>   
>   #define vmstate_offset_macaddr(_state, _field)                       \
> diff --git a/net/net.c b/net/net.c
> index 0e28099..a856907 100644
> --- a/net/net.c
> +++ b/net/net.c
> @@ -1568,25 +1568,31 @@ int net_client_parse(QemuOptsList *opts_list, const char *optarg)
>   
>   /* From FreeBSD */
>   /* XXX: optimize */
> -unsigned compute_mcast_idx(const uint8_t *ep)
> +uint32_t net_crc32(const uint8_t *p, int len)

imho there is no point in using signed length.

>   {
>       uint32_t crc;
>       int carry, i, j;
>       uint8_t b;
>   
>       crc = 0xffffffff;
> -    for (i = 0; i < 6; i++) {
> -        b = *ep++;
> +    for (i = 0; i < len; i++) {
> +        b = *p++;
>           for (j = 0; j < 8; j++) {
>               carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);
>               crc <<= 1;
>               b >>= 1;
>               if (carry) {
> -                crc = ((crc ^ POLYNOMIAL) | carry);
> +                crc = ((crc ^ POLYNOMIAL_BE) | carry);
>               }
>           }
>       }
> -    return crc >> 26;
> +
> +    return crc;
> +}
> +
> +unsigned compute_mcast_idx(const uint8_t *ep)
> +{
> +    return net_crc32(ep, 6) >> 26;

while here let's use ETH_ALEN

>   }
>   
>   QemuOptsList qemu_netdev_opts = {
> 
with "uint32_t net_crc32(const uint8_t *p, size_t len);":
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Philippe Mathieu-Daudé Aug. 18, 2017, 5:06 p.m. UTC | #2 
On 08/18/2017 01:51 PM, Philippe Mathieu-Daudé wrote:
> On 08/18/2017 11:15 AM, Mark Cave-Ayland wrote:
>> Separate out the standard ethernet CRC32 calculation into a new 
>> net_crc32()
>> function, renaming the constant POLYNOMIAL to POLYNOMIAL_BE to make it 
>> clear
>> that this is a big-endian CRC32 calculation.
>>
>> Then remove the existing implementation from compute_mcast_idx() and 
>> call the
>> new function in its place.
>>
>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>> ---
>>   include/net/net.h |    3 ++-
>>   net/net.c         |   16 +++++++++++-----
>>   2 files changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/net/net.h b/include/net/net.h
>> index 1c55a93..586098c 100644
>> --- a/include/net/net.h
>> +++ b/include/net/net.h
>> @@ -227,7 +227,8 @@ NetClientState *net_hub_port_find(int hub_id);
>>   void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd);
>> -#define POLYNOMIAL 0x04c11db6
>> +#define POLYNOMIAL_BE 0x04c11db6
>> +uint32_t net_crc32(const uint8_t *p, int len);
>>   unsigned compute_mcast_idx(const uint8_t *ep);
>>   #define vmstate_offset_macaddr(_state, _field)                       \
>> diff --git a/net/net.c b/net/net.c
>> index 0e28099..a856907 100644
>> --- a/net/net.c
>> +++ b/net/net.c
>> @@ -1568,25 +1568,31 @@ int net_client_parse(QemuOptsList *opts_list, 
>> const char *optarg)
>>   /* From FreeBSD */
>>   /* XXX: optimize */
>> -unsigned compute_mcast_idx(const uint8_t *ep)
>> +uint32_t net_crc32(const uint8_t *p, int len)
> 
> imho there is no point in using signed length.
> 
>>   {
>>       uint32_t crc;
>>       int carry, i, j;
>>       uint8_t b;
>>       crc = 0xffffffff;
>> -    for (i = 0; i < 6; i++) {
>> -        b = *ep++;
>> +    for (i = 0; i < len; i++) {
>> +        b = *p++;
>>           for (j = 0; j < 8; j++) {
>>               carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);
>>               crc <<= 1;
>>               b >>= 1;
>>               if (carry) {
>> -                crc = ((crc ^ POLYNOMIAL) | carry);
>> +                crc = ((crc ^ POLYNOMIAL_BE) | carry);
>>               }
>>           }
>>       }
>> -    return crc >> 26;
>> +
>> +    return crc;
>> +}
>> +
>> +unsigned compute_mcast_idx(const uint8_t *ep)
>> +{
>> +    return net_crc32(ep, 6) >> 26;
> 
> while here let's use ETH_ALEN
>

reading the next patches, what do you think about:

static inline uint32_t mac_crc32_be(const uint8_t *p)
{
     return net_crc32_be(ep, ETH_ALEN);
}

unsigned compute_mcast_idx(const uint8_t *ep)
{
     return mac_crc32_be(p) >> 26;
}

>>   }
>>   QemuOptsList qemu_netdev_opts = {
>>
> with "uint32_t net_crc32(const uint8_t *p, size_t len);":
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Mark Cave-Ayland Aug. 18, 2017, 6:11 p.m. UTC | #3 
On 18/08/17 18:06, Philippe Mathieu-Daudé wrote:

> On 08/18/2017 01:51 PM, Philippe Mathieu-Daudé wrote:
>> On 08/18/2017 11:15 AM, Mark Cave-Ayland wrote:
>>> Separate out the standard ethernet CRC32 calculation into a new
>>> net_crc32()
>>> function, renaming the constant POLYNOMIAL to POLYNOMIAL_BE to make
>>> it clear
>>> that this is a big-endian CRC32 calculation.
>>>
>>> Then remove the existing implementation from compute_mcast_idx() and
>>> call the
>>> new function in its place.
>>>
>>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>>> ---
>>>   include/net/net.h |    3 ++-
>>>   net/net.c         |   16 +++++++++++-----
>>>   2 files changed, 13 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/include/net/net.h b/include/net/net.h
>>> index 1c55a93..586098c 100644
>>> --- a/include/net/net.h
>>> +++ b/include/net/net.h
>>> @@ -227,7 +227,8 @@ NetClientState *net_hub_port_find(int hub_id);
>>>   void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd);
>>> -#define POLYNOMIAL 0x04c11db6
>>> +#define POLYNOMIAL_BE 0x04c11db6
>>> +uint32_t net_crc32(const uint8_t *p, int len);
>>>   unsigned compute_mcast_idx(const uint8_t *ep);
>>>   #define vmstate_offset_macaddr(_state, _field)                       \
>>> diff --git a/net/net.c b/net/net.c
>>> index 0e28099..a856907 100644
>>> --- a/net/net.c
>>> +++ b/net/net.c
>>> @@ -1568,25 +1568,31 @@ int net_client_parse(QemuOptsList *opts_list,
>>> const char *optarg)
>>>   /* From FreeBSD */
>>>   /* XXX: optimize */
>>> -unsigned compute_mcast_idx(const uint8_t *ep)
>>> +uint32_t net_crc32(const uint8_t *p, int len)
>>
>> imho there is no point in using signed length.
>>
>>>   {
>>>       uint32_t crc;
>>>       int carry, i, j;
>>>       uint8_t b;
>>>       crc = 0xffffffff;
>>> -    for (i = 0; i < 6; i++) {
>>> -        b = *ep++;
>>> +    for (i = 0; i < len; i++) {
>>> +        b = *p++;
>>>           for (j = 0; j < 8; j++) {
>>>               carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);
>>>               crc <<= 1;
>>>               b >>= 1;
>>>               if (carry) {
>>> -                crc = ((crc ^ POLYNOMIAL) | carry);
>>> +                crc = ((crc ^ POLYNOMIAL_BE) | carry);
>>>               }
>>>           }
>>>       }
>>> -    return crc >> 26;
>>> +
>>> +    return crc;
>>> +}
>>> +
>>> +unsigned compute_mcast_idx(const uint8_t *ep)
>>> +{
>>> +    return net_crc32(ep, 6) >> 26;
>>
>> while here let's use ETH_ALEN
>>
> 
> reading the next patches, what do you think about:
> 
> static inline uint32_t mac_crc32_be(const uint8_t *p)
> {
>     return net_crc32_be(ep, ETH_ALEN);
> }
> 
> unsigned compute_mcast_idx(const uint8_t *ep)
> {
>     return mac_crc32_be(p) >> 26;
> }

Yes, using ETH_ALEN looks like a good idea - I can do that for the next
revision.

As for the naming of the functions, I've followed the kernel convention
that by default the CRC32 functions are big-endian unless they have a
_le suffix. I don't really feel strongly either way, so I'm happy to go
with whatever naming scheme Jason prefers.


ATB,

Mark.
diff mbox

Patch

diff --git a/include/net/net.h b/include/net/net.h
index 1c55a93..586098c 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -227,7 +227,8 @@  NetClientState *net_hub_port_find(int hub_id);
 
 void qdev_set_nic_properties(DeviceState *dev, NICInfo *nd);
 
-#define POLYNOMIAL 0x04c11db6
+#define POLYNOMIAL_BE 0x04c11db6
+uint32_t net_crc32(const uint8_t *p, int len);
 unsigned compute_mcast_idx(const uint8_t *ep);
 
 #define vmstate_offset_macaddr(_state, _field)                       \
diff --git a/net/net.c b/net/net.c
index 0e28099..a856907 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1568,25 +1568,31 @@  int net_client_parse(QemuOptsList *opts_list, const char *optarg)
 
 /* From FreeBSD */
 /* XXX: optimize */
-unsigned compute_mcast_idx(const uint8_t *ep)
+uint32_t net_crc32(const uint8_t *p, int len)
 {
     uint32_t crc;
     int carry, i, j;
     uint8_t b;
 
     crc = 0xffffffff;
-    for (i = 0; i < 6; i++) {
-        b = *ep++;
+    for (i = 0; i < len; i++) {
+        b = *p++;
         for (j = 0; j < 8; j++) {
             carry = ((crc & 0x80000000L) ? 1 : 0) ^ (b & 0x01);
             crc <<= 1;
             b >>= 1;
             if (carry) {
-                crc = ((crc ^ POLYNOMIAL) | carry);
+                crc = ((crc ^ POLYNOMIAL_BE) | carry);
             }
         }
     }
-    return crc >> 26;
+
+    return crc;
+}
+
+unsigned compute_mcast_idx(const uint8_t *ep)
+{
+    return net_crc32(ep, 6) >> 26;
 }
 
 QemuOptsList qemu_netdev_opts = {