Re: [PATCH] Updating the GEM MAC IP to properly filter out the multicast addresses

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Thu, Nov 28, 2019 at 05:02:00PM +0000, Wasim, Bilal wrote:
> This was one of my first attempts, and so I was sure to miss something.. I've incorporated all the updates in this patch.. Let me know what you think about this.. 
> 
> net/cadence_gem: Updating the GEM MAC IP to properly filter out the multicast addresses.
> 
> The current code makes a bad assumption that the most-significant byte
> of the MAC address is used to determine if the address is multicast or
> unicast, but in reality only a single bit is used to determine this.
> This caused IPv6 to not work.. Fix is now in place and has been tested
> with ZCU102-A53 / IPv6 on a TAP interface. Works well..

Thanks Bilal,

This looks better but not quite there yet.

* You don't seem to be using git-send-email to post patches, try it,
it will make life easier wrt to formatting. The patch should be in a
separate email. The subject line should be the subject of the email.
git-format-patch and git-send-email will take care of that for you.

* You don't need to define IS_MULTICAST, you can directly
use is_multicast_ether_addr() and friends.

* The patch still has long lines (longer than 80 chars)
You can run scripts/checkpatch.pl on your commit before
posting the patch.

Cheers,
Edgar



> 
> Signed-off-by: Bilal Wasim <bilal_wasim@mentor.com>
> ---
>  hw/net/cadence_gem.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c
> index b8be73dc55..98efb93f8a 100644
> --- a/hw/net/cadence_gem.c
> +++ b/hw/net/cadence_gem.c
> @@ -34,6 +34,7 @@
>  #include "qemu/module.h"
>  #include "sysemu/dma.h"
>  #include "net/checksum.h"
> +#include "net/eth.h"
>  
>  #ifdef CADENCE_GEM_ERR_DEBUG
>  #define DB_PRINT(...) do { \
> @@ -315,6 +316,12 @@
>  
>  #define GEM_MODID_VALUE 0x00020118
>  
> +/* IEEE has specified that the most significant bit of the most significant byte be used for
> + * distinguishing between Unicast and Multicast addresses.
> + * If its a 1, that means multicast, 0 means unicast.   */
> +#define IS_MULTICAST(address)           is_multicast_ether_addr(address)
> +#define IS_UNICAST(address)             is_unicast_ether_addr(address)
> +
>  static inline uint64_t tx_desc_get_buffer(CadenceGEMState *s, uint32_t *desc)
>  {
>      uint64_t ret = desc[0];
> @@ -601,7 +608,7 @@ static void gem_receive_updatestats(CadenceGEMState *s, const uint8_t *packet,
>      }
>  
>      /* Error-free Multicast Frames counter */
> -    if (packet[0] == 0x01) {
> +    if (IS_MULTICAST(packet)) {
>          s->regs[GEM_RXMULTICNT]++;
>      }
>  
> @@ -690,21 +697,21 @@ static int gem_mac_address_filter(CadenceGEMState *s, const uint8_t *packet)
>      }
>  
>      /* Accept packets -w- hash match? */
> -    if ((packet[0] == 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_MCAST_HASH)) ||
> -        (packet[0] != 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_UCAST_HASH))) {
> +    if ((IS_MULTICAST(packet) && (s->regs[GEM_NWCFG] & GEM_NWCFG_MCAST_HASH)) ||
> +        (IS_UNICAST(packet)   && (s->regs[GEM_NWCFG] & GEM_NWCFG_UCAST_HASH))) {
>          unsigned hash_index;
>  
>          hash_index = calc_mac_hash(packet);
>          if (hash_index < 32) {
>              if (s->regs[GEM_HASHLO] & (1<<hash_index)) {
> -                return packet[0] == 0x01 ? GEM_RX_MULTICAST_HASH_ACCEPT :
> -                                           GEM_RX_UNICAST_HASH_ACCEPT;
> +                return IS_MULTICAST(packet) ? GEM_RX_MULTICAST_HASH_ACCEPT :
> +                                              GEM_RX_UNICAST_HASH_ACCEPT;
>              }
>          } else {
>              hash_index -= 32;
>              if (s->regs[GEM_HASHHI] & (1<<hash_index)) {
> -                return packet[0] == 0x01 ? GEM_RX_MULTICAST_HASH_ACCEPT :
> -                                           GEM_RX_UNICAST_HASH_ACCEPT;
> +                return IS_MULTICAST(packet) ? GEM_RX_MULTICAST_HASH_ACCEPT :
> +                                              GEM_RX_UNICAST_HASH_ACCEPT;
>              }
>          }
>      }
> -- 
> 2.19.1.windows.1
> 
> ------------------------------------------------------------------------------------------------------------------------------
> -----Original Message-----
> From: Edgar E. Iglesias [mailto:edgar.iglesias@gmail.com] 
> Sent: Thursday, November 28, 2019 9:00 PM
> To: Wasim, Bilal <Bilal_Wasim@mentor.com>
> Cc: qemu-devel@nongnu.org; alistair@alistair23.me; peter.maydell@linaro.org; qemu-arm@nongnu.org
> Subject: Re: [PATCH] Updating the GEM MAC IP to properly filter out the multicast addresses
> 
> On Thu, Nov 28, 2019 at 03:10:16PM +0000, Wasim, Bilal wrote:
> > [PATCH] Updating the GEM MAC IP to properly filter out the multicast 
> > addresses. The current code makes a bad assumption that the 
> > most-significant byte of the MAC address is used to determine if the 
> > address is multicast or unicast, but in reality only a single bit is 
> > used to determine this. This caused IPv6 to not work.. Fix is now in 
> > place and has been tested with
> > ZCU102-A53 / IPv6 on a TAP interface. Works well..
> 
> Hi Bilal,
> 
> The fix looks right to me but I have a few comments.
> 
> * Your patch seems a little wrongly formated.
> [PATCH] goes into the Subject line for example and you're missing path prefixes.
> 
> Do a git log -- hw/net/cadence_gem.c to see examples on how it should look.
> 
> * The patch will probably not pass checkpatch since you seem to have long lines.
> 
> * We also need to update gem_receive_updatestats() to use the corrected macros.
> 
> More inline:
> 
> > 
> > Signed-off-by: Bilal Wasim <bilal_wasim@mentor.com>
> > ---
> > hw/net/cadence_gem.c | 18 ++++++++++++------
> > 1 file changed, 12 insertions(+), 6 deletions(-)
> > 
> > diff --git a/hw/net/cadence_gem.c b/hw/net/cadence_gem.c index 
> > b8be73d..f8bcbb3 100644
> > --- a/hw/net/cadence_gem.c
> > +++ b/hw/net/cadence_gem.c
> > @@ -315,6 +315,12 @@
> >  #define GEM_MODID_VALUE 0x00020118
> > +/* IEEE has specified that the most significant bit of the most 
> > +significant byte be used for
> > + * distinguishing between Unicast and Multicast addresses.
> > + * If its a 1, that means multicast, 0 means unicast.   */
> > +#define IS_MULTICAST(address)           (((address[0] & 0x01) == 0x01) ? 1 : 0)
> 
> 
> 
> This can be simplified:
> #define IS_MULTICAST(address) (address[0] & 1)
> 
> Actually, looking closer, we already have functions to do these checks in:
> include/net/eth.h
> 
> static inline int is_multicast_ether_addr(const uint8_t *addr) static inline int is_broadcast_ether_addr(const uint8_t *addr) static inline int is_unicast_ether_addr(const uint8_t *addr)
> 
> 
> 
> > +#define IS_UNICAST(address)             (!IS_MULTICAST(address))
> > +
> > static inline uint64_t tx_desc_get_buffer(CadenceGEMState *s, uint32_t 
> > *desc) {
> >      uint64_t ret = desc[0];
> > @@ -690,21 +696,21 @@ static int gem_mac_address_filter(CadenceGEMState *s, const uint8_t *packet)
> >      }
> >      /* Accept packets -w- hash match? */
> > -    if ((packet[0] == 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_MCAST_HASH)) ||
> > -        (packet[0] != 0x01 && (s->regs[GEM_NWCFG] & GEM_NWCFG_UCAST_HASH))) {
> > +    if ((IS_MULTICAST(packet) && (s->regs[GEM_NWCFG] & GEM_NWCFG_MCAST_HASH)) ||
> > +        (IS_UNICAST(packet)   && (s->regs[GEM_NWCFG] & GEM_NWCFG_UCAST_HASH))) {
> >          unsigned hash_index;
> >          hash_index = calc_mac_hash(packet);
> >          if (hash_index < 32) {
> >              if (s->regs[GEM_HASHLO] & (1<<hash_index)) {
> > -                return packet[0] == 0x01 ? GEM_RX_MULTICAST_HASH_ACCEPT :
> > -                                           GEM_RX_UNICAST_HASH_ACCEPT;
> > +                return IS_MULTICAST(packet) ? GEM_RX_MULTICAST_HASH_ACCEPT :
> > +                                              
> > + GEM_RX_UNICAST_HASH_ACCEPT;
> >              }
> >          } else {
> >              hash_index -= 32;
> >              if (s->regs[GEM_HASHHI] & (1<<hash_index)) {
> > -                return packet[0] == 0x01 ? GEM_RX_MULTICAST_HASH_ACCEPT :
> > -                                           GEM_RX_UNICAST_HASH_ACCEPT;
> > +                return IS_MULTICAST(packet) ? GEM_RX_MULTICAST_HASH_ACCEPT :
> > +                                              
> > + GEM_RX_UNICAST_HASH_ACCEPT;
> >              }
> >          }
> >      }
> > --
> > 2.9.3
> >