On Thu, May 25, 2017 at 01:05:11PM -0700, Joe Stringer wrote: > On 24 May 2017 at 20:02, Ben Pfaff <[email protected]> wrote: > > On Tue, May 23, 2017 at 04:02:12PM -0700, Joe Stringer wrote: > >> Clang 4.0 complains: > >> > >> ../lib/odp-execute.c:61:37: error: taking address of packed member > >> 'eth_dst' of > >> class or structure 'eth_header' may result in an unaligned pointer value > >> [-Werror,-Waddress-of-packed-member] > >> ether_addr_copy_masked(&eh->eth_src, key->eth_src, > >> mask->eth_src); > >> ^~~~~~~~~~~ > >> ../lib/odp-execute.c:62:37: error: taking address of packed member > >> 'eth_dst' of > >> class or structure 'eth_header' may result in an unaligned pointer value > >> [-Werror,-Waddress-of-packed-member] > >> ether_addr_copy_masked(&eh->eth_dst, key->eth_dst, > >> mask->eth_dst); > >> > >> Ethernet source addresses are 48 bits offset into the Ethernet header, > >> so taking a pointer for this is not guaranteed to be valid on all > >> architectures. Fix this by referencing the memory direct from the > >> Ethernet header pointer. > >> > >> Signed-off-by: Joe Stringer <[email protected]> > > > > I don't understand--why does Clang think that there's something packed > > here? I don't see any packed annotation on struct eth_header (and I > > don't think it needs one). > > https://github.com/openvswitch/ovs/blob/master/lib/packets.h#L398 > > I believe that this is the wire-formatted version that we use for > assembling PDUs for protocols such as STP, so I think it needs to be > properly packed.
Oh, oops, somehow I was blind to the difference between eth_header and eth_addr. But I don't actually see a need to pack this structure. There's nothing in it that would cause a compile to insert padding. It has all 16-bit members (including nested members), and you never get padding (on normal architectures) when all the members of a struct have the same size; otherwise arrays wouldn't work reasonably. I'll send some patches. _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
