[Nmh-workers] Send/post is intolerant of network errors

[Valdis . Kletnieks]

I've hit a corner case of send/post getting confoozled when my VPN
connection died while sending.

Almost certainly relevant is my .mh_profile entry:

post: -msgid -server auth.smtp.vt.edu -port 587 -tls -sasl

My VPN connection evaporated during the send, and post got hung spinning
on 100% CPU time (approx 50% system and 50% user mode).  Tracing with
gdb and catching a stack backtrace several times shows:

gdb) where
#0  0x0000003a975310f4 in __strncpy_ssse3 () from /lib64/libc.so.6
#1  0x0000000000406b5e in smhear ()
#2  0x0000000000407076 in smtalk ()
#3  0x0000000000407792 in sm_wtend ()
#4  0x0000000000403e89 in do_text ()
#5  0x000000000040413f in post ()
#6  0x0000000000405593 in main ()
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0x0000003a975310f4 in __strncpy_ssse3 () from /lib64/libc.so.6
(gdb) where
#0  0x0000003a975310f4 in __strncpy_ssse3 () from /lib64/libc.so.6
#1  0x0000000000406b5e in smhear ()
#2  0x0000000000407076 in smtalk ()
#3  0x0000000000407792 in sm_wtend ()
#4  0x0000000000403e89 in do_text ()
#5  0x000000000040413f in post ()
#6  0x0000000000405593 in main ()
(gdb) ^CQuit
(gdb) c
Continuing.
^C
Program received signal SIGINT, Interrupt.
0x0000003a974d8580 in __read_nocancel () from /lib64/libc.so.6
(gdb) where
#0  0x0000003a974d8580 in __read_nocancel () from /lib64/libc.so.6
#1  0x0000003aa38ad741 in read (__nbytes=5, __buf=0x1620083, 
    __fd=<value optimized out>) at /usr/include/bits/unistd.h:45
#2  sock_read (b=0x1619e30, out=0x1620083 "\027\003\001", outl=5)
    at bss_sock.c:142
#3  0x0000003aa38ab4d9 in BIO_read (b=0x1619e30, out=0x1620083, outl=5)
    at bio_lib.c:212
#4  0x0000003aa8424ee5 in ssl3_read_n (s=0x1619a30, n=5, max=5, 
    extend=<value optimized out>) at s3_pkt.c:238
#5  0x0000003aa8425ebd in ssl3_get_record (s=0x1619a30) at s3_pkt.c:317
#6  ssl3_read_bytes (s=0x1619a30, type=23, 
    buf=0x7fffa2aec050 "address@hidden>... Recipient ok\r\n\227:", 
    len=8192, peek=0) at s3_pkt.c:959
#7  0x0000003aa8423434 in ssl3_read_internal (s=0x1619a30, buf=0x7fffa2aec050, 
    len=8192, peek=0) at s3_lib.c:3265
#8  0x0000000000406786 in sm_fgetc ()
#9  0x0000000000406c1b in smhear ()
#10 0x0000000000407076 in smtalk ()
#11 0x0000000000407792 in sm_wtend ()
#12 0x0000000000403e89 in do_text ()
#13 0x000000000040413f in post ()
#14 0x0000000000405593 in main ()

strace reports us spinning on a read() syscall:
read(3, "", 5)                          = 0
read(3, "", 5)                          = 0
read(3, "", 5)                          = 0
read(3, "", 5)                          = 0
read(3, "", 5)                          = 0

and lsof says that file descriptor is:

post    18463 valdis    3u  sock    0,5      0t0 111223 can't identify protocol

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