On 06/07/13 at 06:24pm, Nicolas Dichtel wrote: > Put Thomas in CC. > > Le 07/06/2013 17:43, Eric Paris a écrit : >> On Fri, 2013-06-07 at 17:25 +0200, Nicolas Dichtel wrote: >> >> NAK. >> >> I tried this once before and as I recal userspace actually expected the >> stoopidity of being unaligned and broke :-( > On which userspace tools do you think? > > For example, in the libnl, the function which tries to get the next > netlink message expects this alignment: You should only align the end of the Netlink message if you append another Netlink message after it. There is no point in aligning it if no message follows in the same buffer. A receiver should never enforce alignment for the last message. Some do and this is causing a lot of pain. An example is the Open vSwitch implementation which stricly enforces alignment of nlmsg_len which makes attempts to implement zerocopy for the upcall more difficult than it should be.