Diff of the two buildlogs:

--
--- b1/build.log	2024-05-14 01:22:12.560267867 +0000
+++ b2/build.log	2024-05-14 01:28:03.209349027 +0000
@@ -1,6 +1,6 @@
 I: pbuilder: network access will be disabled during build
-I: Current time: Sun Jun 15 19:44:12 -12 2025
-I: pbuilder-time-stamp: 1750059852
+I: Current time: Tue May 14 15:22:15 +14 2024
+I: pbuilder-time-stamp: 1715649735
 I: Building the build Environment
 I: extracting base tarball [/var/cache/pbuilder/trixie-reproducible-base.tgz]
 I: copying local configuration
@@ -26,52 +26,84 @@
 dpkg-source: info: unpacking golang-github-xtaci-smux_1.5.16+ds-1.debian.tar.xz
 I: Not using root during the build.
 I: Installing the build-deps
-I: user script /srv/workspace/pbuilder/144598/tmp/hooks/D02_print_environment starting
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/D01_modify_environment starting
+debug: Running on ionos1-amd64.
+I: Changing host+domainname to test build reproducibility
+I: Adding a custom variable just for the fun of it...
+I: Changing /bin/sh to bash
+'/bin/sh' -> '/bin/bash'
+lrwxrwxrwx 1 root root 9 May 14 01:22 /bin/sh -> /bin/bash
+I: Setting pbuilder2's login shell to /bin/bash
+I: Setting pbuilder2's GECOS to second user,second room,second work-phone,second home-phone,second other
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/D01_modify_environment finished
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/D02_print_environment starting
 I: set
-  BUILDDIR='/build/reproducible-path'
-  BUILDUSERGECOS='first user,first room,first work-phone,first home-phone,first other'
-  BUILDUSERNAME='pbuilder1'
-  BUILD_ARCH='amd64'
-  DEBIAN_FRONTEND='noninteractive'
-  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=42 '
-  DISTRIBUTION='trixie'
-  HOME='/root'
-  HOST_ARCH='amd64'
+  BASH=/bin/sh
+  BASHOPTS=checkwinsize:cmdhist:complete_fullquote:extquote:force_fignore:globasciiranges:globskipdots:hostcomplete:interactive_comments:patsub_replacement:progcomp:promptvars:sourcepath
+  BASH_ALIASES=()
+  BASH_ARGC=()
+  BASH_ARGV=()
+  BASH_CMDS=()
+  BASH_LINENO=([0]="12" [1]="0")
+  BASH_LOADABLES_PATH=/usr/local/lib/bash:/usr/lib/bash:/opt/local/lib/bash:/usr/pkg/lib/bash:/opt/pkg/lib/bash:.
+  BASH_SOURCE=([0]="/tmp/hooks/D02_print_environment" [1]="/tmp/hooks/D02_print_environment")
+  BASH_VERSINFO=([0]="5" [1]="2" [2]="21" [3]="1" [4]="release" [5]="x86_64-pc-linux-gnu")
+  BASH_VERSION='5.2.21(1)-release'
+  BUILDDIR=/build/reproducible-path
+  BUILDUSERGECOS='second user,second room,second work-phone,second home-phone,second other'
+  BUILDUSERNAME=pbuilder2
+  BUILD_ARCH=amd64
+  DEBIAN_FRONTEND=noninteractive
+  DEB_BUILD_OPTIONS='buildinfo=+all reproducible=+all parallel=20 '
+  DIRSTACK=()
+  DISTRIBUTION=trixie
+  EUID=0
+  FUNCNAME=([0]="Echo" [1]="main")
+  GROUPS=()
+  HOME=/root
+  HOSTNAME=i-capture-the-hostname
+  HOSTTYPE=x86_64
+  HOST_ARCH=amd64
   IFS=' 	
   '
-  INVOCATION_ID='423649f227304915b938f37d1d3e7558'
-  LANG='C'
-  LANGUAGE='en_US:en'
-  LC_ALL='C'
-  MAIL='/var/mail/root'
-  OPTIND='1'
-  PATH='/usr/sbin:/usr/bin:/sbin:/bin:/usr/games'
-  PBCURRENTCOMMANDLINEOPERATION='build'
-  PBUILDER_OPERATION='build'
-  PBUILDER_PKGDATADIR='/usr/share/pbuilder'
-  PBUILDER_PKGLIBDIR='/usr/lib/pbuilder'
-  PBUILDER_SYSCONFDIR='/etc'
-  PPID='144598'
-  PS1='# '
-  PS2='> '
+  INVOCATION_ID=7fb813c893c748719efe585a9166a98d
+  LANG=C
+  LANGUAGE=et_EE:et
+  LC_ALL=C
+  MACHTYPE=x86_64-pc-linux-gnu
+  MAIL=/var/mail/root
+  OPTERR=1
+  OPTIND=1
+  OSTYPE=linux-gnu
+  PATH=/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path
+  PBCURRENTCOMMANDLINEOPERATION=build
+  PBUILDER_OPERATION=build
+  PBUILDER_PKGDATADIR=/usr/share/pbuilder
+  PBUILDER_PKGLIBDIR=/usr/lib/pbuilder
+  PBUILDER_SYSCONFDIR=/etc
+  PIPESTATUS=([0]="0")
+  POSIXLY_CORRECT=y
+  PPID=2546550
   PS4='+ '
-  PWD='/'
-  SHELL='/bin/bash'
-  SHLVL='2'
-  SUDO_COMMAND='/usr/bin/timeout -k 18.1h 18h /usr/bin/ionice -c 3 /usr/bin/nice /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.wsM5fKuu/pbuilderrc_RZrc --distribution trixie --hookdir /etc/pbuilder/first-build-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/trixie-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.wsM5fKuu/b1 --logfile b1/build.log golang-github-xtaci-smux_1.5.16+ds-1.dsc'
-  SUDO_GID='110'
-  SUDO_UID='105'
-  SUDO_USER='jenkins'
-  TERM='unknown'
-  TZ='/usr/share/zoneinfo/Etc/GMT+12'
-  USER='root'
-  _='/usr/bin/systemd-run'
-  http_proxy='http://213.165.73.152:3128'
+  PWD=/
+  SHELL=/bin/bash
+  SHELLOPTS=braceexpand:errexit:hashall:interactive-comments:posix
+  SHLVL=3
+  SUDO_COMMAND='/usr/bin/timeout -k 24.1h 24h /usr/bin/ionice -c 3 /usr/bin/nice -n 11 /usr/bin/unshare --uts -- /usr/sbin/pbuilder --build --configfile /srv/reproducible-results/rbuild-debian/r-b-build.wsM5fKuu/pbuilderrc_2FVV --distribution trixie --hookdir /etc/pbuilder/rebuild-hooks --debbuildopts -b --basetgz /var/cache/pbuilder/trixie-reproducible-base.tgz --buildresult /srv/reproducible-results/rbuild-debian/r-b-build.wsM5fKuu/b2 --logfile b2/build.log golang-github-xtaci-smux_1.5.16+ds-1.dsc'
+  SUDO_GID=110
+  SUDO_UID=105
+  SUDO_USER=jenkins
+  TERM=unknown
+  TZ=/usr/share/zoneinfo/Etc/GMT-14
+  UID=0
+  USER=root
+  _='I: set'
+  http_proxy=http://46.16.76.132:3128
 I: uname -a
-  Linux ionos5-amd64 6.6.13+bpo-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.6.13-1~bpo12+1 (2024-02-15) x86_64 GNU/Linux
+  Linux i-capture-the-hostname 6.1.0-21-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.90-1 (2024-05-03) x86_64 GNU/Linux
 I: ls -l /bin
-  lrwxrwxrwx 1 root root 7 Jun 13 17:46 /bin -> usr/bin
-I: user script /srv/workspace/pbuilder/144598/tmp/hooks/D02_print_environment finished
+  lrwxrwxrwx 1 root root 7 May 11 11:25 /bin -> usr/bin
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/D02_print_environment finished
  -> Attempting to satisfy build-dependencies
  -> Creating pbuilder-satisfydepends-dummy package
 Package: pbuilder-satisfydepends-dummy
@@ -150,7 +182,7 @@
 Get: 35 http://deb.debian.org/debian trixie/main amd64 golang-go amd64 2:1.22~3 [44.2 kB]
 Get: 36 http://deb.debian.org/debian trixie/main amd64 golang-any amd64 2:1.22~3 [5104 B]
 Get: 37 http://deb.debian.org/debian trixie/main amd64 golang-github-pkg-errors-dev all 0.9.1-3 [12.9 kB]
-Fetched 62.7 MB in 1s (121 MB/s)
+Fetched 62.7 MB in 4s (16.0 MB/s)
 debconf: delaying package configuration, since apt-utils is not installed
 Selecting previously unselected package sensible-utils.
 (Reading database ... 
(Reading database ... 5%
(Reading database ... 10%
(Reading database ... 15%
(Reading database ... 20%
(Reading database ... 25%
(Reading database ... 30%
(Reading database ... 35%
(Reading database ... 40%
(Reading database ... 45%
(Reading database ... 50%
(Reading database ... 55%
(Reading database ... 60%
(Reading database ... 65%
(Reading database ... 70%
(Reading database ... 75%
(Reading database ... 80%
(Reading database ... 85%
(Reading database ... 90%
(Reading database ... 95%
(Reading database ... 100%
(Reading database ... 19699 files and directories currently installed.)
@@ -313,7 +345,11 @@
 Building tag database...
  -> Finished parsing the build-deps
 I: Building the package
-I: Running cd /build/reproducible-path/golang-github-xtaci-smux-1.5.16+ds/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games" HOME="/nonexistent/first-build" dpkg-genchanges -S  > ../golang-github-xtaci-smux_1.5.16+ds-1_source.changes
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/A99_set_merged_usr starting
+Not re-configuring usrmerge for trixie
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/A99_set_merged_usr finished
+hostname: Name or service not known
+I: Running cd /build/reproducible-path/golang-github-xtaci-smux-1.5.16+ds/ && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-buildpackage -us -uc -b && env PATH="/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/i/capture/the/path" HOME="/nonexistent/second-build" dpkg-genchanges -S  > ../golang-github-xtaci-smux_1.5.16+ds-1_source.changes
 dpkg-buildpackage: info: source package golang-github-xtaci-smux
 dpkg-buildpackage: info: source version 1.5.16+ds-1
 dpkg-buildpackage: info: source distribution unstable
@@ -331,28 +367,28 @@
    dh_autoreconf -O--buildsystem=golang
    dh_auto_configure -O--buildsystem=golang
    dh_auto_build -O--buildsystem=golang
-	cd obj-x86_64-linux-gnu && go install -trimpath -v -p 42 github.com/xtaci/smux
-internal/itoa
+	cd obj-x86_64-linux-gnu && go install -trimpath -v -p 20 github.com/xtaci/smux
+unicode/utf8
 internal/nettrace
-internal/goos
 unicode
-unicode/utf8
-cmp
-internal/coverage/rtcov
-internal/race
-internal/unsafeheader
-internal/goexperiment
+internal/goarch
 internal/godebugs
-runtime/internal/atomic
+internal/unsafeheader
+internal/goos
 runtime/internal/syscall
-internal/goarch
-internal/cpu
-math/bits
-sync/atomic
-runtime/internal/math
 internal/chacha8rand
-runtime/internal/sys
+runtime/internal/atomic
+runtime/internal/math
 internal/abi
+runtime/internal/sys
+internal/itoa
+math/bits
+internal/cpu
+internal/race
+cmp
+internal/goexperiment
+internal/coverage/rtcov
+sync/atomic
 slices
 internal/bytealg
 math
@@ -364,15 +400,15 @@
 internal/bisect
 runtime/cgo
 internal/godebug
-errors
 sort
+errors
 io
-internal/intern
 internal/oserror
-path
 internal/safefilepath
-vendor/golang.org/x/net/dns/dnsmessage
 strconv
+internal/intern
+path
+vendor/golang.org/x/net/dns/dnsmessage
 syscall
 container/heap
 net/netip
@@ -380,17 +416,17 @@
 internal/syscall/execenv
 internal/syscall/unix
 time
-context
 io/fs
 internal/poll
-internal/fmtsort
-encoding/binary
+context
 os
+encoding/binary
+internal/fmtsort
 fmt
 net
 github.com/xtaci/smux
    dh_auto_test -O--buildsystem=golang
-	cd obj-x86_64-linux-gnu && go test -vet=off -v -p 42 github.com/xtaci/smux
+	cd obj-x86_64-linux-gnu && go test -vet=off -v -p 20 github.com/xtaci/smux
 === RUN   TestAllocGet
 --- PASS: TestAllocGet (0.00s)
 === RUN   TestAllocPut
@@ -407,23 +443,23 @@
     mux_test.go:73: max stream buffer must not be larger than max receive buffer
 --- PASS: TestConfig (0.00s)
 === RUN   TestEcho
---- PASS: TestEcho (0.01s)
+--- PASS: TestEcho (0.05s)
 === RUN   TestWriteTo
---- PASS: TestWriteTo (0.02s)
+--- PASS: TestWriteTo (0.20s)
 === RUN   TestWriteToV2
---- PASS: TestWriteToV2 (0.02s)
+--- PASS: TestWriteToV2 (0.19s)
 === RUN   TestGetDieCh
---- PASS: TestGetDieCh (0.00s)
+--- PASS: TestGetDieCh (0.02s)
 === RUN   TestSpeed
-    session_test.go:315: 127.0.0.1:50928 127.0.0.1:42609
-    session_test.go:336: time for 16MB rtt 57.761835ms
---- PASS: TestSpeed (0.06s)
+    session_test.go:315: 127.0.0.1:55402 127.0.0.1:36399
+    session_test.go:336: time for 16MB rtt 452.430412ms
+--- PASS: TestSpeed (0.45s)
 === RUN   TestParallel
     session_test.go:374: created 1000 streams
---- PASS: TestParallel (2.21s)
+--- PASS: TestParallel (13.39s)
 === RUN   TestParallelV2
     session_test.go:408: created 1000 streams
---- PASS: TestParallelV2 (2.28s)
+--- PASS: TestParallelV2 (13.93s)
 === RUN   TestCloseThenOpen
 --- PASS: TestCloseThenOpen (0.00s)
 === RUN   TestSessionDoubleClose
@@ -431,21 +467,21 @@
 === RUN   TestStreamDoubleClose
 --- PASS: TestStreamDoubleClose (0.00s)
 === RUN   TestConcurrentClose
---- PASS: TestConcurrentClose (0.00s)
+--- PASS: TestConcurrentClose (0.02s)
 === RUN   TestTinyReadBuffer
---- PASS: TestTinyReadBuffer (0.01s)
+--- PASS: TestTinyReadBuffer (0.04s)
 === RUN   TestIsClose
 --- PASS: TestIsClose (0.00s)
 === RUN   TestKeepAliveTimeout
 --- PASS: TestKeepAliveTimeout (3.00s)
 === RUN   TestKeepAliveBlockWriteTimeout
---- PASS: TestKeepAliveBlockWriteTimeout (3.00s)
+--- PASS: TestKeepAliveBlockWriteTimeout (3.01s)
 === RUN   TestServerEcho
---- PASS: TestServerEcho (0.01s)
+--- PASS: TestServerEcho (0.03s)
 === RUN   TestSendWithoutRecv
---- PASS: TestSendWithoutRecv (0.00s)
+--- PASS: TestSendWithoutRecv (0.02s)
 === RUN   TestWriteAfterClose
---- PASS: TestWriteAfterClose (0.00s)
+--- PASS: TestWriteAfterClose (0.04s)
 === RUN   TestReadStreamAfterSessionClose
     session_test.go:703: EOF
 --- PASS: TestReadStreamAfterSessionClose (0.00s)
@@ -454,9 +490,9 @@
 === RUN   TestNumStreamAfterClose
 --- PASS: TestNumStreamAfterClose (0.00s)
 === RUN   TestRandomFrame
---- PASS: TestRandomFrame (0.01s)
+--- PASS: TestRandomFrame (0.04s)
 === RUN   TestWriteFrameInternal
---- PASS: TestWriteFrameInternal (1.00s)
+--- PASS: TestWriteFrameInternal (1.02s)
 === RUN   TestReadDeadline
 --- PASS: TestReadDeadline (0.00s)
 === RUN   TestWriteDeadline
@@ -469,7 +505,7 @@
     shaper_test.go:29: prio: 100
 --- PASS: TestShaper (0.00s)
 PASS
-ok  	github.com/xtaci/smux	11.636s
+ok  	github.com/xtaci/smux	35.524s
    create-stamp debian/debhelper-build-stamp
    dh_testroot -O--buildsystem=golang
    dh_prep -O--buildsystem=golang
@@ -498,12 +534,14 @@
 dpkg-buildpackage: info: binary-only upload (no source included)
 dpkg-genchanges: info: including full source code in upload
 I: copying local configuration
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/B01_cleanup starting
+I: user script /srv/workspace/pbuilder/2546550/tmp/hooks/B01_cleanup finished
 I: unmounting dev/ptmx filesystem
 I: unmounting dev/pts filesystem
 I: unmounting dev/shm filesystem
 I: unmounting proc filesystem
 I: unmounting sys filesystem
 I: cleaning the build env 
-I: removing directory /srv/workspace/pbuilder/144598 and its subdirectories
-I: Current time: Sun Jun 15 19:45:10 -12 2025
-I: pbuilder-time-stamp: 1750059910
+I: removing directory /srv/workspace/pbuilder/2546550 and its subdirectories
+I: Current time: Tue May 14 15:28:02 +14 2024
+I: pbuilder-time-stamp: 1715650082