Use completely static-sized buffers

(cherry picked from commit 49f90025)
(cherry picked from commit 4007a9d0)
7 jobs for 180-fix-cmsgbuf-usage-v9_12-v9_10 in 6 minutes and 27 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Precheck
passed #20599
linux docker amd64
precheck:debian:sid:amd64

00:00:11

 
  Build
passed #20600
linux docker amd64
build:debian:sid:amd64

00:01:41

passed #20601
linux docker i386
build:debian:sid:i386

00:01:45

 
  Test
passed #20604
linux docker amd64
systemtest:debian:sid:amd64

00:04:03

passed #20605
linux docker i386
systemtest:debian:sid:i386

00:04:25

passed #20602
linux docker amd64
unittest:debian:sid:amd64

00:00:54

passed #20603
linux docker i386
unittest:debian:sid:i386

00:00:50