On Tue, 27 Jun 2023 21:40:14 +0200 Paul Gevers wrote: > Source: nmap, udptunnel > Control: found -1 nmap/7.94+dfsg1-1 > Control: found -1 udptunnel/1.1-9 ... > With a recent upload of nmap the autopkgtest of udptunnel fails in > testing when that autopkgtest is run with the binary packages of nmap > from unstable. It passes when run with only packages from testing.
I think this is likely to be a bug in nmap ncat, when I remove udptunnel from the script by connecting ncat directly to ncat, then the failure still happens with the autopkgtest. I was able to reproduce this issue outside a chroot. I have attached a pair of scripts; bad fails and good succeeds. In the good case, I use `sleep` to hold stdin of `ncat -l` open for 2s, in the bad case I let it use the stdin provided by the shell (a GNOME terminal pty here). Looking at the diff between the verbose logs is interesting. In the good case one select fd is ready and one becomes ready later, the latter one gets used, but in the bad case both fds appear to be ready immediately but neither of them get used. -NCAT DEBUG: select returned 1 fds ready -NCAT DEBUG: fd 3 is ready -NCAT DEBUG: selecting, fdmax 3 -NCAT DEBUG: select returned 1 fds ready +NCAT DEBUG: select returned 2 fds ready So the issue can be worked around in the udptunnel script by piping sleep to the ncat listener instead of launching ncat and then sleeping, or the ncat change that caused this can get bisected and fixed. -- bye, pabs https://wiki.debian.org/PaulWise
bad
Description: application/shellscript
+ rm rx tx + echo foo + sleep 2s + ncat -vvvvvvvvvvvvvvvv -u -l 127.0.0.1 1234 Ncat: Version 7.94 ( https://nmap.org/ncat ) NCAT DEBUG: Initialized fdlist with 102 maxfds Ncat: Listening on 127.0.0.1:1234 NCAT DEBUG: Added fd 3 to list, nfds 1, maxfd 3 NCAT DEBUG: Added fd 0 to list, nfds 2, maxfd 3 NCAT DEBUG: Initialized fdlist with 100 maxfds NCAT DEBUG: selecting, fdmax 3 + ncat -u 127.0.0.1 1234 NCAT DEBUG: select returned 1 fds ready NCAT DEBUG: fd 3 is ready NCAT DEBUG: Swapping fd[0] (3) with fd[1] (0) NCAT DEBUG: Removed fd 3 from list, nfds 1, maxfd 0 Ncat: Connection from 127.0.0.1:57558. NCAT DEBUG: Added fd 3 to list, nfds 2, maxfd 3 NCAT DEBUG: Added fd 3 to list, nfds 1, maxfd 3 NCAT DEBUG: selecting, fdmax 3 NCAT DEBUG: select returned 2 fds ready NCAT DEBUG: fd 0 is ready NCAT DEBUG: EOF on stdin + sleep 2s + head -vn-0 tx rx ==> tx <== foo ==> rx <== + echo tx tx + hd tx 00000000 66 6f 6f 0a |foo.| 00000004 + echo rx rx + hd rx + echo diff diff + diff -u tx rx --- tx 2023-07-23 16:49:32.411502343 +0800 +++ rx 2023-07-23 16:49:32.411502343 +0800 @@ -1 +0,0 @@ -foo
good
Description: application/shellscript
+ rm rx tx + echo foo + + sleep 2sncat -u 127.0.0.1 1234 + ncat -vvvvvvvvvvvvvvvv -u -l 127.0.0.1 1234 Ncat: Version 7.94 ( https://nmap.org/ncat ) NCAT DEBUG: Initialized fdlist with 102 maxfds Ncat: Listening on 127.0.0.1:1234 NCAT DEBUG: Added fd 3 to list, nfds 1, maxfd 3 NCAT DEBUG: Added fd 0 to list, nfds 2, maxfd 3 NCAT DEBUG: Initialized fdlist with 100 maxfds NCAT DEBUG: selecting, fdmax 3 NCAT DEBUG: select returned 1 fds ready NCAT DEBUG: fd 3 is ready NCAT DEBUG: Swapping fd[0] (3) with fd[1] (0) NCAT DEBUG: Removed fd 3 from list, nfds 1, maxfd 0 Ncat: Connection from 127.0.0.1:36688. NCAT DEBUG: Added fd 3 to list, nfds 2, maxfd 3 NCAT DEBUG: Added fd 3 to list, nfds 1, maxfd 3 NCAT DEBUG: selecting, fdmax 3 NCAT DEBUG: select returned 1 fds ready NCAT DEBUG: fd 3 is ready NCAT DEBUG: selecting, fdmax 3 + sleep 2s NCAT DEBUG: select returned 1 fds ready NCAT DEBUG: fd 0 is ready NCAT DEBUG: EOF on stdin + head -vn-0 tx rx ==> tx <== foo ==> rx <== foo + echo tx tx + hd tx 00000000 66 6f 6f 0a |foo.| 00000004 + echo rx rx + hd rx 00000000 66 6f 6f 0a |foo.| 00000004 + echo diff diff + diff -u tx rx
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