If I have a IPsec rule like:
spdadd 192.168.7.8 1.2.3.4 any -P out ipsec esp/transport//require;
(i.e. a remote host 1.2.3.4 which will not respond)
Then any attempt to communicate with 1.2.3.4 will block, even when using
non-blocking sockets:
socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 3
setsockopt(3, SOL_SOCKET, SO_LINGER, {onoff=1, linger=0}, 8) = 0
setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
fcntl64(3, F_GETFL) = 0x2 (flags O_RDWR)
fcntl64(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0 <-- non-blocking socket
connect(3, {sa_family=AF_INET, sin_port=htons(22),
sin_addr=inet_addr("1.2.3.4")}, 16 <-- blocked connect()
[277657.564773] netcat S b06bcf20 0 9450 9449
[277657.564785] c8d51d28 00200046 00200046 b06bcf20 00200286 c8d51d14
00200286 c8d51d84
[277657.564814] b06bcf20 c8d51d28 b013680b c8d51d84 eeae8800 c8d51d78
c8d51dd0 b04d3fc5
[277657.564843] c8d51da4 00000002 00000001 ede87284 00000002 00000040
e9318ac0 db3f20a0
[277657.564874] Call Trace:
[277657.564881] [<b04d3fc5>] __xfrm_lookup+0x2f5/0x510
[277657.564905] [<b0494f9e>] ip_route_output_flow+0x4e/0x80
[277657.564919] [<b04af303>] tcp_v4_connect+0x183/0x6d0
[277657.564934] [<b04beaf2>] inet_stream_connect+0x122/0x1c0
[277657.564949] [<b0471c8e>] sys_connect+0x9e/0xd0
[277657.564963] [<b0472785>] sys_socketcall+0xa5/0x230
[277657.564973] [<b01042ba>] syscall_call+0x7/0xb
[277657.564984] =======================
I had a process using non-blocking sockets stuck in connect() for over 8 hours
because of this...
00002630 <__xfrm_lookup>:
...
290b: b8 00 00 00 00 mov $0x0,%eax
290c: R_386_32 km_waitq
2910: e8 fc ff ff ff call 2911 <__xfrm_lookup+0x2e1>
2911: R_386_PC32 add_wait_queue
2915: a1 00 00 00 00 mov 0x0,%eax
2916: R_386_32 per_cpu__current_task
291a: c7 00 01 00 00 00 movl $0x1,(%eax)
2920: e8 fc ff ff ff call 2921 <__xfrm_lookup+0x2f1>
2921: R_386_PC32 schedule
2925: a1 00 00 00 00 mov 0x0,%eax
2926: R_386_32 per_cpu__current_task
292a: c7 00 00 00 00 00 movl $0x0,(%eax)
2930: b8 00 00 00 00 mov $0x0,%eax
2931: R_386_32 km_waitq
2935: 89 da mov %ebx,%edx
2937: e8 fc ff ff ff call 2938 <__xfrm_lookup+0x308>
2938: R_386_PC32 remove_wait_queue
--
Simon Arlott
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