Brenden Blanco [Thu, 27 Aug 2015 07:59:34 +0000 (00:59 -0700)]
Merge pull request #168 from iovisor/weichunc_dev
Add gretap support for full mesh tunnel
Wei-Chun Chao [Wed, 26 Aug 2015 21:57:21 +0000 (14:57 -0700)]
Add gretap support for full mesh tunnel
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
4ast [Wed, 26 Aug 2015 14:49:41 +0000 (07:49 -0700)]
Merge pull request #166 from iovisor/bblanco_dev
Add proper debian build support, rename libbcc.so
Brenden Blanco [Wed, 26 Aug 2015 13:46:37 +0000 (06:46 -0700)]
Merge pull request #167 from brendangregg/master
improve examples using new features
Brendan Gregg [Wed, 26 Aug 2015 10:16:29 +0000 (20:16 +1000)]
improve code by utilizing trace_readline_fields()
Brendan Gregg [Wed, 26 Aug 2015 10:15:18 +0000 (20:15 +1000)]
improve code by utilizing .clear()
Brenden Blanco [Wed, 26 Aug 2015 07:13:23 +0000 (00:13 -0700)]
Support versioning out of git tree in debuild
This adds support for properly tagging the build when cmake is run not
in a git tree, which is the case when building from src-deb.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Wed, 26 Aug 2015 06:14:25 +0000 (23:14 -0700)]
Add proper debian build support
The cmake based build system is nice, but not quite production ready.
Move to the more painful but featureful debuild style. This is one step
towards an upstreamable package.
Rename libbpfprog (ugh) to libbcc.
Split out python-bpf and libbcc-examples into separate packages that
depend on libbcc.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Wed, 26 Aug 2015 05:43:22 +0000 (22:43 -0700)]
Merge pull request #165 from iovisor/bblanco_dev
Fix print() breakage in python 2.7 environments
Brenden Blanco [Wed, 26 Aug 2015 05:40:21 +0000 (22:40 -0700)]
Fix print() breakage in python 2.7 environments
Fixes: #164
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Tue, 25 Aug 2015 14:36:16 +0000 (07:36 -0700)]
Merge pull request #163 from iovisor/bblanco_dev
Add debug flag to enable prints from kernel verifier
Brenden Blanco [Tue, 25 Aug 2015 06:55:59 +0000 (23:55 -0700)]
test_trace4 is unreliable, use a different test regex
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Tue, 25 Aug 2015 06:42:42 +0000 (23:42 -0700)]
Add debug flag to enable prints from kernel verifier
Add flag to BPF() to enable debug prints from the verifier. Use by
passing 0x2 to debug= in the constructor. Add docstring for BPF
constructor.
Also, optimize bpf_prog_load so that by default the kernel is not
asked to print the verbose output. The program will be "loaded" a second
time to capture the verifier failure message.
Fixes: #147
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Tue, 25 Aug 2015 05:02:49 +0000 (22:02 -0700)]
Merge pull request #162 from iovisor/bblanco_dev
Add regex support to attach_k[ret]probe
Brenden Blanco [Tue, 25 Aug 2015 04:33:25 +0000 (21:33 -0700)]
Add regex support to attach_k[ret]probe
Add new event_re parameter to kprobe functions. This searches through
the list of functions/symbols in <tracefs>/available_filter_functions
for all matching functions. Every one is attached.
Add a test case for attach_k[ret]probe.
Fixes: #141
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
yonghong-song [Mon, 24 Aug 2015 23:15:48 +0000 (16:15 -0700)]
Merge pull request #161 from svinota/master
examples: use IPDB `wait_ip()` feature
Peter V. Saveliev [Mon, 24 Aug 2015 19:55:35 +0000 (21:55 +0200)]
examples: use IPDB `wait_ip()` feature
4ast [Mon, 24 Aug 2015 19:23:09 +0000 (12:23 -0700)]
Merge pull request #160 from iovisor/bblanco_dev
Add field support to trace_print and friends
Brenden Blanco [Mon, 24 Aug 2015 19:06:36 +0000 (12:06 -0700)]
Add field support to trace_print and friends
Add trace_readline_fields helper to parse the output of trace_pipe
Add field parsing support to trace_print. Addresses #149.
Fix typo in trace_open s/trace/tracefile/
Make nonblocking=False the default in trace_readline
Use IOError vs BlockingIOError for greater compatibility (untested)
Fixes: #149
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Mon, 24 Aug 2015 16:55:57 +0000 (09:55 -0700)]
Merge pull request #158 from iovisor/bblanco_dev
Fix map.clear() usage for array type maps
Brenden Blanco [Mon, 24 Aug 2015 05:59:38 +0000 (22:59 -0700)]
Fix map.clear() usage for array type maps
Calling delete on an array type map entry does not have an effect.
Instead, the entry needs to be zeroed out, since the array slot always
exists. To avoid unnecessary calls to update(), only call update() when
the map type is array-like. The type was not exposed to python up until
now, so add it.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Sat, 22 Aug 2015 16:55:09 +0000 (09:55 -0700)]
Merge pull request #157 from iovisor/bblanco_dev
Add test case for clearing of maps from python
Brenden Blanco [Sat, 22 Aug 2015 15:33:29 +0000 (08:33 -0700)]
Add test case for clearing of maps from python
Fixes: #142
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Fri, 21 Aug 2015 23:37:01 +0000 (16:37 -0700)]
Merge pull request #156 from iovisor/bblanco_dev
Add BPF python helpers for reading trace_pipe
Brenden Blanco [Fri, 21 Aug 2015 23:33:02 +0000 (16:33 -0700)]
Add BPF python helpers for reading trace_pipe
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Thu, 20 Aug 2015 19:56:35 +0000 (12:56 -0700)]
Merge pull request #153 from brendangregg/master
more examples of b[] syntax, fix func arg passing
Brendan Gregg [Thu, 20 Aug 2015 19:52:30 +0000 (12:52 -0700)]
tidier example
Brendan Gregg [Thu, 20 Aug 2015 19:40:37 +0000 (12:40 -0700)]
more examples of b[] syntax, fix func arg passing
4ast [Thu, 20 Aug 2015 18:46:42 +0000 (11:46 -0700)]
Merge pull request #152 from iovisor/bblanco_dev
Add getitem api to BPF object to reference tables
Brenden Blanco [Thu, 20 Aug 2015 18:27:21 +0000 (11:27 -0700)]
Add getitem api to BPF object to reference tables
To simplify some common usage patterns, add a getitem api to the BPF
class. This wraps the get_table() api and allows the api user to skip
keeping their own get_table handle.
Fixes: #137
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Wed, 19 Aug 2015 22:48:30 +0000 (15:48 -0700)]
Merge pull request #151 from iovisor/bblanco_dev
Change API of attach_kprobe to take a name argument
Brenden Blanco [Wed, 19 Aug 2015 22:39:19 +0000 (15:39 -0700)]
Change API of attach_kprobe to take a name argument
Per feedback on the attach_kprobe api, change up the arguments to remove
the load_func that typically preceeds the call. Instead, move this
inside the attach_kprobe implementation. Also, this makes attach_kprobe
need to be non-static. The same applies to attach_kretprobe.
Old:
fn = b.load_func("hello", BPF.KPROBE)
BPF.attach_kprobe(fn, "sys_clone")
New:
b.attach_kprobe(event="sys_clone", fn_name="hello")
Note that the kwarg style is not required, but I fixed up the current
usages to provide readability.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Wed, 19 Aug 2015 00:55:32 +0000 (17:55 -0700)]
Merge pull request #150 from brendangregg/master
some bcc examples and tools
Brendan Gregg [Tue, 18 Aug 2015 23:53:41 +0000 (16:53 -0700)]
save some syscalls
Brendan Gregg [Tue, 18 Aug 2015 23:49:48 +0000 (16:49 -0700)]
python 2 & 3 compatibility
Brendan Gregg [Tue, 18 Aug 2015 23:11:35 +0000 (16:11 -0700)]
support odd Linux distros
Brendan Gregg [Tue, 18 Aug 2015 22:34:56 +0000 (15:34 -0700)]
cleaner get_table calls
Brendan Gregg [Tue, 18 Aug 2015 22:17:29 +0000 (15:17 -0700)]
include paths
Brendan Gregg [Tue, 18 Aug 2015 21:56:14 +0000 (14:56 -0700)]
some bcc examples and tools
4ast [Mon, 17 Aug 2015 17:32:28 +0000 (10:32 -0700)]
Merge pull request #134 from iovisor/bblanco_dev
Add format string argument to bpf-run
Brenden Blanco [Mon, 17 Aug 2015 17:24:20 +0000 (10:24 -0700)]
Add format string argument to bpf-run
Usage:
bpf-run -f "time={3} output={5}"
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Mon, 17 Aug 2015 16:41:04 +0000 (09:41 -0700)]
Merge pull request #133 from iovisor/bblanco_dev
Add bpf-run command line tool
Brenden Blanco [Mon, 17 Aug 2015 16:37:30 +0000 (09:37 -0700)]
Add bpf-run command line tool
Example usage:
sudo bpf-run -p sys_clone -c 'bpf_trace_printk("Hello, World!\n");' -t
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Mon, 17 Aug 2015 03:06:35 +0000 (20:06 -0700)]
Merge pull request #132 from iovisor/yhs_dev
add dhcp support for tunnel-mesh
Yonghong Song [Thu, 13 Aug 2015 10:04:40 +0000 (03:04 -0700)]
add dhcp support for tunnel-mesh
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
Brenden Blanco [Thu, 13 Aug 2015 00:33:18 +0000 (17:33 -0700)]
Merge pull request #130 from iovisor/yhs_dev
add vlan_learning and distributed_bridge in libbcc package
Brenden Blanco [Thu, 13 Aug 2015 00:32:19 +0000 (17:32 -0700)]
Merge pull request #131 from iovisor/weichunc_dev
distributed_bridge: check ip address before validating traffic
Wei-Chun Chao [Thu, 13 Aug 2015 00:13:24 +0000 (17:13 -0700)]
distributed_bridge: check ip address before validating traffic
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
Yonghong Song [Thu, 13 Aug 2015 00:08:39 +0000 (17:08 -0700)]
add vlan_learning and distributed_bridge in libbcc package
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
Brenden Blanco [Wed, 12 Aug 2015 23:25:31 +0000 (16:25 -0700)]
Merge pull request #129 from iovisor/weichunc_dev
distributed_bridge: wait for ns comes up before validating traffic
Wei-Chun Chao [Wed, 12 Aug 2015 23:04:06 +0000 (16:04 -0700)]
distributed_bridge: wait for ns comes up before validating traffic
Sometimes it takes longer for ns to complete configuration.
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
Brenden Blanco [Wed, 12 Aug 2015 20:14:24 +0000 (13:14 -0700)]
Merge pull request #128 from iovisor/weichunc_dev
test_brb2: only account for IP and ARP packets
4ast [Wed, 12 Aug 2015 20:09:35 +0000 (13:09 -0700)]
Merge pull request #127 from iovisor/bblanco_dev
Changes to support map entry read/write in fuse
Wei-Chun Chao [Wed, 12 Aug 2015 20:08:08 +0000 (13:08 -0700)]
test_brb2: only account for IP and ARP packets
Sometimes background noise fails the test
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
Brenden Blanco [Wed, 12 Aug 2015 19:08:00 +0000 (12:08 -0700)]
Add testing for scanf/printf in python, deprecate table_update
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Wed, 12 Aug 2015 15:55:09 +0000 (08:55 -0700)]
Add sscanf C api for parsing key/leaf ascii to binary
Expose an individual API of the what is done in table_update, that lets
the caller use the module to parse keys for it.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Wed, 12 Aug 2015 15:25:50 +0000 (08:25 -0700)]
Merge pull request #126 from iovisor/yhs_dev
clean up potential conflict veth before creating new one in create_ns
Yonghong Song [Wed, 12 Aug 2015 15:21:57 +0000 (08:21 -0700)]
close ipr to avoid fd leak
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
Yonghong Song [Tue, 11 Aug 2015 02:04:58 +0000 (19:04 -0700)]
use pyroute2 IProute to remove the stale veth
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
4ast [Wed, 12 Aug 2015 01:41:35 +0000 (18:41 -0700)]
Merge pull request #125 from iovisor/bblanco_dev
Add printf for key/leaf and fix trace_printk bug
Brenden Blanco [Wed, 12 Aug 2015 01:33:49 +0000 (18:33 -0700)]
Support nested rewrite of trace arguments in bpf_trace_printk
There was an issue where the rewrite of bpf_trace_printk combined with
conversion of function argument to ctx->$reg was mangling the text. Fix
up this case and add a test.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Tue, 11 Aug 2015 16:30:13 +0000 (09:30 -0700)]
Add printf key/leaf writer functionality
This extends upon the sscanf reader functionality, with the intent of
providing key/leaf pretty printing
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Tue, 11 Aug 2015 20:07:27 +0000 (13:07 -0700)]
Merge pull request #123 from iovisor/bblanco_dev
Fix recursive loop in parsing pointer to self struct
Brenden Blanco [Tue, 11 Aug 2015 19:45:00 +0000 (12:45 -0700)]
Fix recursive loop in parsing pointer to self struct
Issue occurs in the description visitor class, when the struct used in a
map key is a pointer to self, as in:
struct node;
struct node {
struct node *next;
};
Avoid this in the desc by using "unsigned long long" for all pointers.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Yonghong Song [Tue, 11 Aug 2015 00:33:24 +0000 (17:33 -0700)]
clean up potential conflict veth before creating new one in create_ns
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
Brenden Blanco [Mon, 10 Aug 2015 19:06:06 +0000 (12:06 -0700)]
Merge pull request #122 from iovisor/yhs_dev2
Fixing more ctrl-c problem
Brenden Blanco [Mon, 10 Aug 2015 19:05:06 +0000 (12:05 -0700)]
Merge pull request #121 from iovisor/weichunc_dev
add connectivity validation in distributed bridge examples
Brenden Blanco [Mon, 10 Aug 2015 19:04:27 +0000 (12:04 -0700)]
Merge pull request #120 from iovisor/yhs_dev
Add one line desc output for simple_tc
Wei-Chun Chao [Mon, 10 Aug 2015 18:56:14 +0000 (11:56 -0700)]
add connectivity validation in distributed bridge examples
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
Yonghong Song [Mon, 10 Aug 2015 18:35:28 +0000 (11:35 -0700)]
Fixing more ctrl-c problem
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
Yonghong Song [Mon, 10 Aug 2015 18:19:53 +0000 (11:19 -0700)]
print out simple_tc success at the end of test
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
Yonghong Song [Mon, 10 Aug 2015 16:40:11 +0000 (09:40 -0700)]
Add one line desc output for simple_tc
o Also suggest task_switch.py to try with libbcc package
Signed-off-by: Yonghong Song <yhs@plumgrid.com>
4ast [Mon, 10 Aug 2015 05:51:52 +0000 (22:51 -0700)]
Merge pull request #119 from iovisor/bblanco_dev
Patch series: reorganize bpf_module and add sscanf feature for fuse
Brenden Blanco [Sun, 9 Aug 2015 04:21:26 +0000 (21:21 -0700)]
Cleanup some flags left on during development
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Sun, 9 Aug 2015 04:00:59 +0000 (21:00 -0700)]
Add update_table API: accepts sscanf style strings and populates a map
This is the culmination of the previous patches. It adds an api that can
input map data in a string format, but validating the numbers and
locations of data fields. The use case is for fuse file input/output. A
printf api may follow.
Take the table with key/leaf of:
struct Key { int a; int b; };
struct Leaf { int a; int b; int c; struct SubLeaf { int x; int y; } s; };
One would input to this table using:
update_table(table_name, "{1 2}", "{1 2 -3 {9 0xa}}");
The implementation uses a JITed function for each unique type, that is
invoked to run sscanf on behalf of the caller. The input must have the
exact right number of arguments. Bit fields are supported, but the
caller must be aware of the collapse of those bitfields into an aligned
field, as well as endianness.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Sat, 8 Aug 2015 05:04:56 +0000 (22:04 -0700)]
Convert bpf_module structures to use vector instead of map for tables
It was bothering me that a whole bunch of accesses to the tables were
based on a string hash lookup, in addition to the vectors that were kept
to convert ids to names. Switch those around, as well as the api
internally.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Sat, 8 Aug 2015 04:25:46 +0000 (21:25 -0700)]
Remove some deprecated checks in bpf_module
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Sat, 8 Aug 2015 04:04:35 +0000 (21:04 -0700)]
Add LLVM IR based sscanf routine, to be run by the JIT
After the modules have been created, create a helper function for each
table leaf/key type.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Fri, 7 Aug 2015 16:59:48 +0000 (09:59 -0700)]
Rename BPFTable to TableDesc
This whole project is about bpf, prefixing everything with the same
acronym is redundant.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Fri, 7 Aug 2015 16:56:46 +0000 (09:56 -0700)]
Extract table types from B programs as well
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Fri, 7 Aug 2015 15:28:02 +0000 (08:28 -0700)]
Add framework to support map string reader (fuse feature)
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Wed, 5 Aug 2015 22:23:42 +0000 (15:23 -0700)]
Merge pull request #118 from iovisor/bblanco_dev
Add cmake checks for required test programs
Brenden Blanco [Wed, 5 Aug 2015 22:17:50 +0000 (15:17 -0700)]
Change wording to "Recommended"
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Wed, 5 Aug 2015 22:09:17 +0000 (15:09 -0700)]
Add cmake checks for required test programs
Set as warning, since the build will still work fine and be able to
create a binary package.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Wed, 5 Aug 2015 22:06:44 +0000 (15:06 -0700)]
Merge pull request #117 from iovisor/bblanco_dev
Move helper.h prototype for tail call into 4.2 section
Brenden Blanco [Wed, 5 Aug 2015 21:00:48 +0000 (14:00 -0700)]
Move helper.h prototype for tail call into 4.2 section
With #115, bpf_tail_call was incorrectly disabled in 4.2 builds.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
4ast [Wed, 5 Aug 2015 19:13:36 +0000 (12:13 -0700)]
Merge pull request #116 from iovisor/bblanco_dev
Add INSTALL.md instructions for using Ubuntu binary build
Brenden Blanco [Wed, 5 Aug 2015 19:09:59 +0000 (12:09 -0700)]
Add INSTALL.md instructions for using Ubuntu binary build
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Wed, 5 Aug 2015 13:42:45 +0000 (06:42 -0700)]
Merge pull request #115 from iovisor/bblanco_dev
Flags for 4.3 were accidentally committed, revert
Brenden Blanco [Tue, 4 Aug 2015 23:57:14 +0000 (16:57 -0700)]
Flags for 4.3 were accidentally committed, revert
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Tue, 4 Aug 2015 23:56:46 +0000 (16:56 -0700)]
Merge pull request #114 from iovisor/weichunc_dev
release IPDB in host ns early
Wei-Chun Chao [Tue, 4 Aug 2015 23:29:11 +0000 (16:29 -0700)]
release IPDB in host ns early
We need it for setting vxlan flow based flags currently. Release
it once the interfaces are set up. This does not help Ctrl-C on
main.py though.
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
weichunc [Tue, 4 Aug 2015 22:50:33 +0000 (15:50 -0700)]
Merge pull request #113 from iovisor/bblanco_dev
Suggest Release and add X86 target in readme
Brenden Blanco [Tue, 4 Aug 2015 22:44:20 +0000 (15:44 -0700)]
Suggest Release and add X86 target in readme
The default CMAKE_BUILD_TYPE is Debug when cloning from git, suggest
Release instead.
Also, there are some worrisome warnings during cmake when X86 target is
omitted. Additionally, I may want X86 target support for a future
feature, so lets suggest it here.
Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Brenden Blanco [Tue, 4 Aug 2015 22:30:21 +0000 (15:30 -0700)]
Merge pull request #112 from iovisor/weichunc_dev
llvm 3.7+ deb is broken
Wei-Chun Chao [Tue, 4 Aug 2015 22:26:18 +0000 (15:26 -0700)]
llvm 3.7+ deb is broken
https://llvm.org/bugs/show_bug.cgi?id=24154
Build from source until it's resolved. Another plan is to provide
binary package.
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
Brenden Blanco [Tue, 4 Aug 2015 22:24:26 +0000 (15:24 -0700)]
Merge pull request #110 from iovisor/yhs_dev
better clean up of created namespace/interfaces if ctrl-c is pressed
Brenden Blanco [Tue, 4 Aug 2015 22:17:17 +0000 (15:17 -0700)]
Merge pull request #111 from iovisor/weichunc_dev
fix tunnel_mesh.py
Wei-Chun Chao [Tue, 4 Aug 2015 22:14:28 +0000 (15:14 -0700)]
fix tunnel_mesh.py
The IP assignment was wrong.
Signed-off-by: Wei-Chun Chao <weichunc@plumgrid.com>
Yonghong Song [Tue, 4 Aug 2015 18:10:31 +0000 (11:10 -0700)]
better clean up of created namespace/interfaces if ctrl-c is pressed
o There are still some cases when ctrl-c is pressed, the program does not exit
gracefully, with a however lower probability. In my random manual experiments,
one in ten cases it still hangs and needs further ctrl-z.
Signed-off-by: Yonghong Song <yhs@plumgrid.com>