ether: mark ethernet addresses as being 2-byte aligned
Checks
Commit Message
When including the rte_ether.h header in applications with warnings
enabled, a warning was given because of the assumption of 2-byte alignment
of ethernet addresses when processing them.
.../include/rte_ether.h:149:2: warning: converting a packed ‘const
struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
{aka ‘const short unsigned int’} pointer (alignment 2) may result in
an unaligned pointer value [-Waddress-of-packed-member]
149 | const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
| ^~~~~
Since ethernet addresses should always be aligned on a two-byte boundary,
we can just inform the compiler of this assumption to remove the warnings
and allow us to always access the addresses using 16-bit operations.
Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
---
Although this is an ABI break, the network structures are all being renamed
in this release, and a deprecation notice was previously posted for it.
---
lib/librte_net/rte_ether.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
Comments
On 16/05/2019 16:54, Bruce Richardson wrote:
> When including the rte_ether.h header in applications with warnings
> enabled, a warning was given because of the assumption of 2-byte alignment
> of ethernet addresses when processing them.
>
> .../include/rte_ether.h:149:2: warning: converting a packed ‘const
> struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
> {aka ‘const short unsigned int’} pointer (alignment 2) may result in
> an unaligned pointer value [-Waddress-of-packed-member]
> 149 | const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
> | ^~~~~
>
Hi - There was a couple of these warnings in telemetry that were not
squashed with the patch to disable the warning in 19.05. I was just
about send a patch to address that when I saw this one.
As your patch is aiming for a better solution, I won't send my patch for
master but I'll still send to stable.
> Since ethernet addresses should always be aligned on a two-byte boundary,
> we can just inform the compiler of this assumption to remove the warnings
> and allow us to always access the addresses using 16-bit operations.
>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
>
> ---
>
> Although this is an ABI break, the network structures are all being renamed
> in this release, and a deprecation notice was previously posted for it.
> ---
> lib/librte_net/rte_ether.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
> index 3a87ff184..8090b7c01 100644
> --- a/lib/librte_net/rte_ether.h
> +++ b/lib/librte_net/rte_ether.h
> @@ -55,7 +55,8 @@ extern "C" {
> * See http://standards.ieee.org/regauth/groupmac/tutorial.html
> */
> struct ether_addr {
> - uint8_t addr_bytes[ETHER_ADDR_LEN]; /**< Addr bytes in tx order */
> + /** Addr bytes in tx order */
> + uint8_t addr_bytes[ETHER_ADDR_LEN] __rte_aligned(2);
> } __attribute__((__packed__));
>
> #define ETHER_LOCAL_ADMIN_ADDR 0x02 /**< Locally assigned Eth. address. */
>
On Thu, May 16, 2019 at 07:04:03PM +0100, Kevin Traynor wrote:
> On 16/05/2019 16:54, Bruce Richardson wrote:
> > When including the rte_ether.h header in applications with warnings
> > enabled, a warning was given because of the assumption of 2-byte alignment
> > of ethernet addresses when processing them.
> >
> > .../include/rte_ether.h:149:2: warning: converting a packed ‘const
> > struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
> > {aka ‘const short unsigned int’} pointer (alignment 2) may result in
> > an unaligned pointer value [-Waddress-of-packed-member]
> > 149 | const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
> > | ^~~~~
> >
>
> Hi - There was a couple of these warnings in telemetry that were not
> squashed with the patch to disable the warning in 19.05. I was just
> about send a patch to address that when I saw this one.
>
> As your patch is aiming for a better solution, I won't send my patch for
> master but I'll still send to stable.
>
Good idea, thanks.
Hi Bruce,
On Thu, May 16, 2019 at 04:54:57PM +0100, Bruce Richardson wrote:
> When including the rte_ether.h header in applications with warnings
> enabled, a warning was given because of the assumption of 2-byte alignment
> of ethernet addresses when processing them.
>
> .../include/rte_ether.h:149:2: warning: converting a packed ‘const
> struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
> {aka ‘const short unsigned int’} pointer (alignment 2) may result in
> an unaligned pointer value [-Waddress-of-packed-member]
> 149 | const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
> | ^~~~~
>
> Since ethernet addresses should always be aligned on a two-byte boundary,
I'm a bit reserved about this last assumption. The ethernet address
structure may be used in a private structure, whose alignment is 1. Are
we sure that there is no (funny) protocol that carries unaligned
ethernet addresses?
Shouldn't we change the definition of unaligned_uint16_t instead?
Or change the rte_is_broadcast_ether_addr() function?
> we can just inform the compiler of this assumption to remove the warnings
> and allow us to always access the addresses using 16-bit operations.
>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
>
> ---
>
> Although this is an ABI break, the network structures are all being renamed
> in this release, and a deprecation notice was previously posted for it.
Yes, but the network renaming is identified in the release note as an
API break, not an ABI break.
> ---
> lib/librte_net/rte_ether.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
> index 3a87ff184..8090b7c01 100644
> --- a/lib/librte_net/rte_ether.h
> +++ b/lib/librte_net/rte_ether.h
> @@ -55,7 +55,8 @@ extern "C" {
> * See http://standards.ieee.org/regauth/groupmac/tutorial.html
> */
> struct ether_addr {
> - uint8_t addr_bytes[ETHER_ADDR_LEN]; /**< Addr bytes in tx order */
> + /** Addr bytes in tx order */
> + uint8_t addr_bytes[ETHER_ADDR_LEN] __rte_aligned(2);
> } __attribute__((__packed__));
>
> #define ETHER_LOCAL_ADMIN_ADDR 0x02 /**< Locally assigned Eth. address. */
> --
> 2.21.0
>
On Mon, Jul 01, 2019 at 03:11:12PM +0200, Olivier Matz wrote:
> Hi Bruce,
>
> On Thu, May 16, 2019 at 04:54:57PM +0100, Bruce Richardson wrote:
> > When including the rte_ether.h header in applications with warnings
> > enabled, a warning was given because of the assumption of 2-byte alignment
> > of ethernet addresses when processing them.
> >
> > .../include/rte_ether.h:149:2: warning: converting a packed ‘const
> > struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
> > {aka ‘const short unsigned int’} pointer (alignment 2) may result in
> > an unaligned pointer value [-Waddress-of-packed-member]
> > 149 | const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
> > | ^~~~~
> >
> > Since ethernet addresses should always be aligned on a two-byte boundary,
>
> I'm a bit reserved about this last assumption. The ethernet address
> structure may be used in a private structure, whose alignment is 1. Are
> we sure that there is no (funny) protocol that carries unaligned
> ethernet addresses?
>
> Shouldn't we change the definition of unaligned_uint16_t instead?
> Or change the rte_is_broadcast_ether_addr() function?
>
We could, but I believe the correct behaviour is to make the addresses
always 2-byte aligned, unless someone actually has a real-world case where
there is a protocol that doesn't have the data 2-byte aligned.
/Bruce
Hi Bruce,
On Mon, Jul 01, 2019 at 02:38:43PM +0100, Bruce Richardson wrote:
> On Mon, Jul 01, 2019 at 03:11:12PM +0200, Olivier Matz wrote:
> > Hi Bruce,
> >
> > On Thu, May 16, 2019 at 04:54:57PM +0100, Bruce Richardson wrote:
> > > When including the rte_ether.h header in applications with warnings
> > > enabled, a warning was given because of the assumption of 2-byte alignment
> > > of ethernet addresses when processing them.
> > >
> > > .../include/rte_ether.h:149:2: warning: converting a packed ‘const
> > > struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
> > > {aka ‘const short unsigned int’} pointer (alignment 2) may result in
> > > an unaligned pointer value [-Waddress-of-packed-member]
> > > 149 | const unaligned_uint16_t *ea_words = (const unaligned_uint16_t *)ea;
> > > | ^~~~~
> > >
> > > Since ethernet addresses should always be aligned on a two-byte boundary,
> >
> > I'm a bit reserved about this last assumption. The ethernet address
> > structure may be used in a private structure, whose alignment is 1. Are
> > we sure that there is no (funny) protocol that carries unaligned
> > ethernet addresses?
> >
> > Shouldn't we change the definition of unaligned_uint16_t instead?
> > Or change the rte_is_broadcast_ether_addr() function?
> >
>
> We could, but I believe the correct behaviour is to make the addresses
> always 2-byte aligned, unless someone actually has a real-world case where
> there is a protocol that doesn't have the data 2-byte aligned.
Maybe you missed that part of my previous answer, I'm copy it again here:
> Although this is an ABI break, the network structures are all being renamed
> in this release, and a deprecation notice was previously posted for it.
Yes, but the network renaming is identified in the release note as an
API break, not an ABI break.
I thought we agreed to limit ABI breakages to cases where there is no
other solution. Here, this is surely a "small" ABI breakage, but I
suppose there is a way to do differently.
If we really want to do that way, it's better to announce it as an ABI
break.
Olivier
On Mon, Jul 01, 2019 at 04:14:30PM +0200, Olivier Matz wrote:
> Hi Bruce,
>
> On Mon, Jul 01, 2019 at 02:38:43PM +0100, Bruce Richardson wrote:
> > On Mon, Jul 01, 2019 at 03:11:12PM +0200, Olivier Matz wrote:
> > > Hi Bruce,
> > >
> > > On Thu, May 16, 2019 at 04:54:57PM +0100, Bruce Richardson wrote:
> > > > When including the rte_ether.h header in applications with warnings
> > > > enabled, a warning was given because of the assumption of 2-byte
> > > > alignment of ethernet addresses when processing them.
> > > >
> > > > .../include/rte_ether.h:149:2: warning: converting a packed ‘const
> > > > struct ether_addr’ pointer (alignment 1) to a ‘unaligned_uint16_t’
> > > > {aka ‘const short unsigned int’} pointer (alignment 2) may result
> > > > in an unaligned pointer value [-Waddress-of-packed-member] 149 |
> > > > const unaligned_uint16_t *ea_words = (const unaligned_uint16_t
> > > > *)ea; | ^~~~~
> > > >
> > > > Since ethernet addresses should always be aligned on a two-byte
> > > > boundary,
> > >
> > > I'm a bit reserved about this last assumption. The ethernet address
> > > structure may be used in a private structure, whose alignment is 1.
> > > Are we sure that there is no (funny) protocol that carries unaligned
> > > ethernet addresses?
> > >
> > > Shouldn't we change the definition of unaligned_uint16_t instead? Or
> > > change the rte_is_broadcast_ether_addr() function?
> > >
> >
> > We could, but I believe the correct behaviour is to make the addresses
> > always 2-byte aligned, unless someone actually has a real-world case
> > where there is a protocol that doesn't have the data 2-byte aligned.
>
> Maybe you missed that part of my previous answer, I'm copy it again here:
>
> > Although this is an ABI break, the network structures are all being
> > renamed in this release, and a deprecation notice was previously
> > posted for it.
>
> Yes, but the network renaming is identified in the release note as an
> API break, not an ABI break.
>
> I thought we agreed to limit ABI breakages to cases where there is no
> other solution. Here, this is surely a "small" ABI breakage, but I
> suppose there is a way to do differently.
>
> If we really want to do that way, it's better to announce it as an ABI
> break.
>
At this stage, I'm ok with pushing this to 19.11 to follow the official
deprecation process.
On Wed, Feb 05, 2020 at 01:21:54AM +0100, Martins Eglitis wrote:
> Dear Bruce and Kevin,
>
> I tried building an application (NFF-GO) which has DPDK as a dependency.
> I am still getting the same warnings you and Kevin were discussing. My
> current DPDK version is 19.11-1.
>
> Do you know if this issue has been resolved?
>
> This is the output:
>
> # github.com/intel-go/nff-go/internal/low
> In file included from
> /home/zebra/Projects/nff-go/dpdk/dpdk/x86_64-native-linuxapp-gcc-install/usr/local/share/dpdk/x86_64-native-linuxapp-gcc/include/rte_ethdev.h:160,
> from
> ../../go/pkg/mod/github.com/intel-go/nff-go@v0.9.1/internal/low/low.h:11,
> from
> ../../go/pkg/mod/github.com/intel-go/nff-go@v0.9.1/internal/low/low.go:16:
> /home/zebra/Projects/nff-go/dpdk/dpdk/x86_64-native-linuxapp-gcc-install/usr/local/share/dpdk/x86_64-native-linuxapp-gcc/include/rte_ether.h:
> In function ‘rte_is_same_ether_addr’:
> /home/zebra/Projects/nff-go/dpdk/dpdk/x86_64-native-linuxapp-gcc-install/usr/local/share/dpdk/x86_64-native-linuxapp-gcc/include/rte_ether.h:84:2:
> warning: converting a packed ‘const struct rte_ether_addr’ pointer
> (alignment 1) to a ‘unaligned_uint16_t’ {aka ‘const short unsigned int’}
> pointer (alignment 2) may result in an unaligned pointer value
> [-Waddress-of-packed-member]
> 84 | const unaligned_uint16_t *w1 = (const uint16_t *)ea1;
> | ^~~~~
<snip>
>
Hi,
looking at the code in DPDK for 19.11, rte_ether.h no longer has the
unaligned_uint16_t type in rte_ether.h. For example, line 84 of rte_ether.h
should read as below:
81 static inline int rte_is_same_ether_addr(const struct rte_ether_addr *ea1,
82 const struct rte_ether_addr *ea2)
83 {
84 const uint16_t *w1 = (const uint16_t *)ea1;
85 const uint16_t *w2 = (const uint16_t *)ea2;
86
Have you got mixed header files from two different DPDK releases?
/Bruce
Hi,
Thank you for the help. I think it has something to do how the NFF-Go is
being built. Will address the question to NFF-Go devs.
Thank you,
Martins
On 2020-02-05 14:45, Bruce Richardson wrote:
> On Wed, Feb 05, 2020 at 01:21:54AM +0100, Martins Eglitis wrote:
>> Dear Bruce and Kevin,
>>
>> I tried building an application (NFF-GO) which has DPDK as a dependency.
>> I am still getting the same warnings you and Kevin were discussing. My
>> current DPDK version is 19.11-1.
>>
>> Do you know if this issue has been resolved?
>>
>> This is the output:
>>
>> # github.com/intel-go/nff-go/internal/low
>> In file included from
>> /home/zebra/Projects/nff-go/dpdk/dpdk/x86_64-native-linuxapp-gcc-install/usr/local/share/dpdk/x86_64-native-linuxapp-gcc/include/rte_ethdev.h:160,
>> from
>> ../../go/pkg/mod/github.com/intel-go/nff-go@v0.9.1/internal/low/low.h:11,
>> from
>> ../../go/pkg/mod/github.com/intel-go/nff-go@v0.9.1/internal/low/low.go:16:
>> /home/zebra/Projects/nff-go/dpdk/dpdk/x86_64-native-linuxapp-gcc-install/usr/local/share/dpdk/x86_64-native-linuxapp-gcc/include/rte_ether.h:
>> In function ‘rte_is_same_ether_addr’:
>> /home/zebra/Projects/nff-go/dpdk/dpdk/x86_64-native-linuxapp-gcc-install/usr/local/share/dpdk/x86_64-native-linuxapp-gcc/include/rte_ether.h:84:2:
>> warning: converting a packed ‘const struct rte_ether_addr’ pointer
>> (alignment 1) to a ‘unaligned_uint16_t’ {aka ‘const short unsigned int’}
>> pointer (alignment 2) may result in an unaligned pointer value
>> [-Waddress-of-packed-member]
>> 84 | const unaligned_uint16_t *w1 = (const uint16_t *)ea1;
>> | ^~~~~
> <snip>
> Hi,
>
> looking at the code in DPDK for 19.11, rte_ether.h no longer has the
> unaligned_uint16_t type in rte_ether.h. For example, line 84 of rte_ether.h
> should read as below:
>
> 81 static inline int rte_is_same_ether_addr(const struct rte_ether_addr *ea1,
> 82 const struct rte_ether_addr *ea2)
> 83 {
> 84 const uint16_t *w1 = (const uint16_t *)ea1;
> 85 const uint16_t *w2 = (const uint16_t *)ea2;
> 86
>
> Have you got mixed header files from two different DPDK releases?
>
> /Bruce
@@ -55,7 +55,8 @@ extern "C" {
* See http://standards.ieee.org/regauth/groupmac/tutorial.html
*/
struct ether_addr {
- uint8_t addr_bytes[ETHER_ADDR_LEN]; /**< Addr bytes in tx order */
+ /** Addr bytes in tx order */
+ uint8_t addr_bytes[ETHER_ADDR_LEN] __rte_aligned(2);
} __attribute__((__packed__));
#define ETHER_LOCAL_ADMIN_ADDR 0x02 /**< Locally assigned Eth. address. */