[PATCH 0/2] BCC: python: support fmod_ret

[PATCH 0/2] BCC: python: support fmod_ret

[Gang Yan]

Support fmod_ret, and add a useful tool for mptcp, also
the interface can be verified with this function.

Gang Yan (2):
  BCC: Python: Support 'fmod_ret' method for eBPF
  BCC: python: add a useful tool for mptcp

 src/python/bcc/__init__.py | 43 ++++++++++++++++++++
 tools/mptcpboost.py        | 82 ++++++++++++++++++++++++++++++++++++++
 tools/mptcpboost.txt       | 22 ++++++++++
 3 files changed, 147 insertions(+)
 create mode 100644 tools/mptcpboost.py
 create mode 100644 tools/mptcpboost.txt

-- 
2.25.1

[PATCH 1/2] BCC: Python: Support 'fmod_ret' method for eBPF

[Gang Yan]

In kernel, there exists a lot of 'fmod_ret' functions, such as
'update_socket_protocol'. But it cannot be attached in BCC-python
directly, so this patch provides an interface for Python to use
'fmod_ret' attaching method.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 src/python/bcc/__init__.py | 43 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/src/python/bcc/__init__.py b/src/python/bcc/__init__.py
index 8bc85516..96de3d40 100644
--- a/src/python/bcc/__init__.py
+++ b/src/python/bcc/__init__.py
@@ -461,6 +461,7 @@ class BPF(object):
         self.raw_tracepoint_fds = {}
         self.kfunc_entry_fds = {}
         self.kfunc_exit_fds = {}
+        self.fmod_ret_fds = {}
         self.lsm_fds = {}
         self.perf_buffers = {}
         self.open_perf_events = {}
@@ -1157,6 +1158,21 @@ class BPF(object):
             return True
         return False
 
+    @staticmethod
+    def support_fmod_ret():
+        if not BPF.support_kfunc():
+            return False
+
+        kernel_version = platform.release()
+        major, minor, _ = kernel_version.split(".")
+
+        if int(major) > 5:
+            return True
+        elif int(major) ==5 and int(minor) >= 6:
+            return True
+        else:
+            return False
+
     def detach_kfunc(self, fn_name=b""):
         fn_name = _assert_is_bytes(fn_name)
         fn_name = BPF.add_prefix(b"kfunc__", fn_name)
@@ -1166,6 +1182,15 @@ class BPF(object):
         os.close(self.kfunc_entry_fds[fn_name])
         del self.kfunc_entry_fds[fn_name]
 
+    def detach_fmod_ret(self, fn_name=b""):
+        fn_name = _assert_is_bytes(fn_name)
+        fn_name = BPF.add_prefix(b"kmod_ret__", fn_name)
+
+        if fn_name not in self.fmod_ret_fds:
+            raise Exception("Fmod_ret func %s is not attached" % fn_name)
+        os.close(self.fmod_ret_fds[fn_name])
+        del self.fmod_ret_fds[fn_name]
+
     def detach_kretfunc(self, fn_name=b""):
         fn_name = _assert_is_bytes(fn_name)
         fn_name = BPF.add_prefix(b"kretfunc__", fn_name)
@@ -1189,6 +1214,22 @@ class BPF(object):
         self.kfunc_entry_fds[fn_name] = fd
         return self
 
+    def attach_fmod_ret(self, fn_name=b""):
+        fn_name = _assert_is_bytes(fn_name)
+        fn_name = BPF.add_prefix(b"kmod_ret__", fn_name)
+
+        if fn_name in self.fmod_ret_fds:
+            raise Exception("Fmod_ret func %s has been attached" % fn_name)
+
+        fn = self.load_func(fn_name, BPF.TRACING)
+        fd = lib.bpf_attach_kfunc(fn.fd)
+
+        if fd < 0:
+            raise Exception("Failed to attach BPF to fmod_ret kernel func")
+        self.fmod_ret_fds[fn_name] = fd
+
+        return self
+
     def attach_kretfunc(self, fn_name=b""):
         fn_name = _assert_is_bytes(fn_name)
         fn_name = BPF.add_prefix(b"kretfunc__", fn_name)
@@ -1824,6 +1865,8 @@ class BPF(object):
             self.detach_kretfunc(k)
         for k, v in list(self.lsm_fds.items()):
             self.detach_lsm(k)
+        for k, v in list(self.fmod_ret_fds.items()):
+            self.detach_fmod_ret(k)
 
         # Clean up opened perf ring buffer and perf events
         table_keys = list(self.tables.keys())
-- 
2.25.1

Re: [PATCH 1/2] BCC: Python: Support 'fmod_ret' method for eBPF

[Matthieu Baerts]

Hi Gang,

On 07/04/2025 04:37, Gang Yan wrote:
> In kernel, there exists a lot of 'fmod_ret' functions, such as
> 'update_socket_protocol'. But it cannot be attached in BCC-python
> directly, so this patch provides an interface for Python to use
> 'fmod_ret' attaching method.
> 
> Signed-off-by: Gang Yan <yangang@kylinos.cn>
> ---
>  src/python/bcc/__init__.py | 43 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/src/python/bcc/__init__.py b/src/python/bcc/__init__.py
> index 8bc85516..96de3d40 100644
> --- a/src/python/bcc/__init__.py
> +++ b/src/python/bcc/__init__.py
> @@ -461,6 +461,7 @@ class BPF(object):
>          self.raw_tracepoint_fds = {}
>          self.kfunc_entry_fds = {}
>          self.kfunc_exit_fds = {}
> +        self.fmod_ret_fds = {}
>          self.lsm_fds = {}
>          self.perf_buffers = {}
>          self.open_perf_events = {}
> @@ -1157,6 +1158,21 @@ class BPF(object):
>              return True
>          return False
>  
> +    @staticmethod
> +    def support_fmod_ret():
> +        if not BPF.support_kfunc():
> +            return False
> +
> +        kernel_version = platform.release()
> +        major, minor, _ = kernel_version.split(".")
> +
> +        if int(major) > 5:
> +            return True
> +        elif int(major) ==5 and int(minor) >= 6:

Was it not introduced in v5.7 instead of v5.6?

  return int(major) > 5 or (int(major) == 5 and int(minor) >= 7)


https://lore.kernel.org/20200304191853.1529-1-kpsingh@chromium.org


But also, it feels wrong to look at the kernel version, in case of
backports, etc. Can you not look at something else? e.g. kallsyms?

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Re: [PATCH 1/2] BCC: Python: Support 'fmod_ret' method for eBPF

[Gang Yan]

On Mon, Apr 07, 2025 at 11:07:41AM +0200, Matthieu Baerts wrote:
Hi Matt,


> Hi Gang,
> 
> On 07/04/2025 04:37, Gang Yan wrote:
> > In kernel, there exists a lot of 'fmod_ret' functions, such as
> > 'update_socket_protocol'. But it cannot be attached in BCC-python
> > directly, so this patch provides an interface for Python to use
> > 'fmod_ret' attaching method.
> > 
> > Signed-off-by: Gang Yan <yangang@kylinos.cn>
> > ---
> >  src/python/bcc/__init__.py | 43 ++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 43 insertions(+)
> > 
> > diff --git a/src/python/bcc/__init__.py b/src/python/bcc/__init__.py
> > index 8bc85516..96de3d40 100644
> > --- a/src/python/bcc/__init__.py
> > +++ b/src/python/bcc/__init__.py
> > @@ -461,6 +461,7 @@ class BPF(object):
> >          self.raw_tracepoint_fds = {}
> >          self.kfunc_entry_fds = {}
> >          self.kfunc_exit_fds = {}
> > +        self.fmod_ret_fds = {}
> >          self.lsm_fds = {}
> >          self.perf_buffers = {}
> >          self.open_perf_events = {}
> > @@ -1157,6 +1158,21 @@ class BPF(object):
> >              return True
> >          return False
> >  
> > +    @staticmethod
> > +    def support_fmod_ret():
> > +        if not BPF.support_kfunc():
> > +            return False
> > +
> > +        kernel_version = platform.release()
> > +        major, minor, _ = kernel_version.split(".")
> > +
> > +        if int(major) > 5:
> > +            return True
> > +        elif int(major) ==5 and int(minor) >= 6:
> 
> Was it not introduced in v5.7 instead of v5.6?
> 
>   return int(major) > 5 or (int(major) == 5 and int(minor) >= 7)
> 
I think v5.7 is right, the 5.6 is from the bcc repo:

bcc/example/cpp/KModRetExample.cc:
	 * Kfunc modify_ret support is only available at kernel version 5.6 and later.

Maybe this is also need to be fixed later?

> 
> https://lore.kernel.org/20200304191853.1529-1-kpsingh@chromium.org
> 
> 
> But also, it feels wrong to look at the kernel version, in case of
> backports, etc. Can you not look at something else? e.g. kallsyms?
>

Do you think we can do this after making a PR first?

> Cheers,
> Matt
> -- 
> Sponsored by the NGI0 Core fund.
> 
> 

Re: [PATCH 1/2] BCC: Python: Support 'fmod_ret' method for eBPF

[Matthieu Baerts]

Hi Gang,

On 08/04/2025 03:56, Gang Yan wrote:
> On Mon, Apr 07, 2025 at 11:07:41AM +0200, Matthieu Baerts wrote:
> Hi Matt,
> 
> 
>> Hi Gang,
>>
>> On 07/04/2025 04:37, Gang Yan wrote:
>>> In kernel, there exists a lot of 'fmod_ret' functions, such as
>>> 'update_socket_protocol'. But it cannot be attached in BCC-python
>>> directly, so this patch provides an interface for Python to use
>>> 'fmod_ret' attaching method.
>>>
>>> Signed-off-by: Gang Yan <yangang@kylinos.cn>
>>> ---
>>>  src/python/bcc/__init__.py | 43 ++++++++++++++++++++++++++++++++++++++
>>>  1 file changed, 43 insertions(+)
>>>
>>> diff --git a/src/python/bcc/__init__.py b/src/python/bcc/__init__.py
>>> index 8bc85516..96de3d40 100644
>>> --- a/src/python/bcc/__init__.py
>>> +++ b/src/python/bcc/__init__.py
>>> @@ -461,6 +461,7 @@ class BPF(object):
>>>          self.raw_tracepoint_fds = {}
>>>          self.kfunc_entry_fds = {}
>>>          self.kfunc_exit_fds = {}
>>> +        self.fmod_ret_fds = {}
>>>          self.lsm_fds = {}
>>>          self.perf_buffers = {}
>>>          self.open_perf_events = {}
>>> @@ -1157,6 +1158,21 @@ class BPF(object):
>>>              return True
>>>          return False
>>>  
>>> +    @staticmethod
>>> +    def support_fmod_ret():
>>> +        if not BPF.support_kfunc():

(I don't know if this dependence is needed here.)

>>> +            return False
>>> +
>>> +        kernel_version = platform.release()
>>> +        major, minor, _ = kernel_version.split(".")
>>> +
>>> +        if int(major) > 5:
>>> +            return True
>>> +        elif int(major) ==5 and int(minor) >= 6:
>>
>> Was it not introduced in v5.7 instead of v5.6?
>>
>>   return int(major) > 5 or (int(major) == 5 and int(minor) >= 7)
>>
> I think v5.7 is right, the 5.6 is from the bcc repo:
> 
> bcc/example/cpp/KModRetExample.cc:
> 	 * Kfunc modify_ret support is only available at kernel version 5.6 and later.
> 
> Maybe this is also need to be fixed later?

Maybe this bit is supported since v5.6 and fmod_ret from 5.7? I didn't
check.

>> https://lore.kernel.org/20200304191853.1529-1-kpsingh@chromium.org
>>
>>
>> But also, it feels wrong to look at the kernel version, in case of
>> backports, etc. Can you not look at something else? e.g. kallsyms?
>>
> 
> Do you think we can do this after making a PR first?

I don't know the BCC project, but I think checking the version will not
be accepted. I think it would be better to do something like that instead:

  @staticmethod
  def support_fmod_ret():
      # It is not clear what can be used to check if 'fmod_ret'
      # supported by the kernel. Assuming checking kfunc is enough.
      return BPF.support_kfunc():

And add a note about that in the commit message, asking BCC devs for
ideas. You can also say you considered checking the kernel version.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

[PATCH 2/2] BCC: python: add a useful tool for mptcp

[Gang Yan]

Multipath TCP (MPTCP) is an extension of the standard TCP protocol
that allows a single transport connection to use multiple network
interfaces. MPTCP is useful for applications like bandwidth
aggregation, failover, and more resilient connections.

Linux kernel starts to support MPTCP since v5.6, this patch provides
a method which can easily force applications use MPTCP socket without
modifing its code.

Signed-off-by: Gang Yan <yangang@kylinos.cn>
---
 tools/mptcpboost.py  | 82 ++++++++++++++++++++++++++++++++++++++++++++
 tools/mptcpboost.txt | 22 ++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 tools/mptcpboost.py
 create mode 100644 tools/mptcpboost.txt

diff --git a/tools/mptcpboost.py b/tools/mptcpboost.py
new file mode 100644
index 00000000..0ddd731a
--- /dev/null
+++ b/tools/mptcpboost.py
@@ -0,0 +1,82 @@
+#!/usr/bin/env python
+#
+# mptcpboost Make the applications to use MPTCP.
+#           For Linux, uses BCC, eBPF. Embedded C.
+#
+# USAGE: mptcpboost -t
+#
+# Copyright 2025 Kylin Software, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License")
+#
+# 05-Apr-2025   Gang Yan   Created this.
+
+import ctypes as ct
+import argparse
+import signal
+import time
+
+from bcc import BPF
+
+#arguments
+parser = argparse.ArgumentParser(
+         description="mptcpboost try to force applications use MPTCP")
+parser.add_argument("-t", "--targets", required=True, type=str,
+                    help="use ',' for multi targets, eg: 'iperf3,rsync'")
+
+args_str = parser.parse_args()
+args_list = [t.strip() for t in args_str.targets.split(',')]
+
+if (not BPF.support_fmod_ret()):
+    print("Your kernel version is too old,"
+          " fmod_ret method is only support kernel v5.6 and later.")
+    exit()
+
+TASK_COMM_LEN = 18
+
+class app_name(ct.Structure):
+    _fields_ = [("str", ct.c_char * TASK_COMM_LEN)]
+
+# define BPF program
+prog = """
+#include <linux/net.h>
+#include <uapi/linux/in.h>
+#include <linux/string.h>
+
+struct app_name {
+    char name[TASK_COMM_LEN];
+};
+
+BPF_HASH(support_apps, struct app_name);
+
+KMOD_RET(update_socket_protocol, int family, int type, int protocol, int ret)
+{
+    struct app_name target = {};
+    bpf_get_current_comm(&target.name, TASK_COMM_LEN);
+
+    if ((family == AF_INET || family == AF_INET6) &&
+        type == SOCK_STREAM &&
+        (!protocol || protocol ==IPPROTO_TCP) &&
+        support_apps.lookup(&target))
+        return IPPROTO_MPTCP;
+
+    return protocol;
+
+}
+
+"""
+
+b = BPF(text=prog)
+b.attach_fmod_ret("update_socket_protocol")
+
+support_apps = b.get_table("support_apps")
+for i in args_list:
+    app = i.encode()
+    name = app_name()
+    name.str = app[:TASK_COMM_LEN-1].ljust(TASK_COMM_LEN, b'\0')
+    support_apps[name] = ct.c_uint32(1)
+
+print("MPTCP is been applied in ", args_list);
+signal.pause()
+#while(1):
+#   time.sleep(200)
+
diff --git a/tools/mptcpboost.txt b/tools/mptcpboost.txt
new file mode 100644
index 00000000..114a1c8b
--- /dev/null
+++ b/tools/mptcpboost.txt
@@ -0,0 +1,22 @@
+Demonstrations of mptcpboost, the Linux eBPF/bcc version.
+
+
+mptcpboost forces the application to use MPTCP instead of TCP.
+
+mptcpboost has been verified with iperf3 and rsync[TCP module]. It can be used
+for incresing the speed of transferring data with rsync.
+
+The MPTCP configuration is decribed in
+https://www.mptcp.dev/pm.html
+
+USAGE message:
+
+usage: test.py [-h] -t TARGETS
+
+mptcpboost try to force applications use MPTCP
+
+options:
+  -h, --help            show this help message and exit
+  -t TARGETS, --targets TARGETS
+                        use ',' for multi targets, eg: 'iperf3,rsync'
+
-- 
2.25.1

Re: [PATCH 2/2] BCC: python: add a useful tool for mptcp

[Matthieu Baerts]

Hi Gang,

On 07/04/2025 04:37, Gang Yan wrote:
> Multipath TCP (MPTCP) is an extension of the standard TCP protocol
> that allows a single transport connection to use multiple network
> interfaces. MPTCP is useful for applications like bandwidth
> aggregation, failover, and more resilient connections.
> 
> Linux kernel starts to support MPTCP since v5.6, this patch provides
> a method which can easily force applications use MPTCP socket without
> modifing its code.
> 
> Signed-off-by: Gang Yan <yangang@kylinos.cn>
> ---
>  tools/mptcpboost.py  | 82 ++++++++++++++++++++++++++++++++++++++++++++
>  tools/mptcpboost.txt | 22 ++++++++++++

Small detail: what about re-using the "mptcpify" name

https://elixir.bootlin.com/linux/latest/source/tools/testing/selftests/bpf/progs/mptcpify.c
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=ddba122428a7

Once applied on BCC side, we could update our website to point to this
program:

  https://www.mptcp.dev/setup.html#force-applications-to-use-mptcp

>  2 files changed, 104 insertions(+)
>  create mode 100644 tools/mptcpboost.py
>  create mode 100644 tools/mptcpboost.txt
> 
> diff --git a/tools/mptcpboost.py b/tools/mptcpboost.py
> new file mode 100644
> index 00000000..0ddd731a
> --- /dev/null
> +++ b/tools/mptcpboost.py
> @@ -0,0 +1,82 @@
> +#!/usr/bin/env python
> +#
> +# mptcpboost Make the applications to use MPTCP.
> +#           For Linux, uses BCC, eBPF. Embedded C.
> +#
> +# USAGE: mptcpboost -t
> +#
> +# Copyright 2025 Kylin Software, Inc.
> +# Licensed under the Apache License, Version 2.0 (the "License")
> +#
> +# 05-Apr-2025   Gang Yan   Created this.
> +
> +import ctypes as ct
> +import argparse
> +import signal
> +import time
> +
> +from bcc import BPF
> +
> +#arguments
> +parser = argparse.ArgumentParser(
> +         description="mptcpboost try to force applications use MPTCP")

detail: 'to' missing: try to force applications *to* use MPTCP

Maybe clearer if we add 'instead of TCP'?

> +parser.add_argument("-t", "--targets", required=True, type=str,
> +                    help="use ',' for multi targets, eg: 'iperf3,rsync'")

Could it be eventually optional to force all apps from the same CGroup
to use MPTCP instead of TCP?


Another idea is to restrict this transformation to the app passed in
argument, e.g.

  mptcpify -- iperf3 -s

(but can be done later if this makes sense)

> +
> +args_str = parser.parse_args()
> +args_list = [t.strip() for t in args_str.targets.split(',')]
> +
> +if (not BPF.support_fmod_ret()):
> +    print("Your kernel version is too old,"
> +          " fmod_ret method is only support kernel v5.6 and later.")

v5.7?

> +    exit()
> +
> +TASK_COMM_LEN = 18
> +
> +class app_name(ct.Structure):
> +    _fields_ = [("str", ct.c_char * TASK_COMM_LEN)]
> +
> +# define BPF program
> +prog = """
> +#include <linux/net.h>
> +#include <uapi/linux/in.h>
> +#include <linux/string.h>
> +
> +struct app_name {
> +    char name[TASK_COMM_LEN];
> +};
> +
> +BPF_HASH(support_apps, struct app_name);
> +
> +KMOD_RET(update_socket_protocol, int family, int type, int protocol, int ret)
> +{
> +    struct app_name target = {};
> +    bpf_get_current_comm(&target.name, TASK_COMM_LEN);
> +
> +    if ((family == AF_INET || family == AF_INET6) &&
> +        type == SOCK_STREAM &&
> +        (!protocol || protocol ==IPPROTO_TCP) &&

detail: space missing after '=='

> +        support_apps.lookup(&target))
> +        return IPPROTO_MPTCP;
> +
> +    return protocol;
> +
> +}
> +
> +"""
> +
> +b = BPF(text=prog)
> +b.attach_fmod_ret("update_socket_protocol")
> +
> +support_apps = b.get_table("support_apps")
> +for i in args_list:
> +    app = i.encode()
> +    name = app_name()
> +    name.str = app[:TASK_COMM_LEN-1].ljust(TASK_COMM_LEN, b'\0')
> +    support_apps[name] = ct.c_uint32(1)
> +
> +print("MPTCP is been applied in ", args_list);

detail: MPTCP is being forced for:

> +signal.pause()
> +#while(1):
> +#   time.sleep(200)

I guess you can remove the comments.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Re: [PATCH 2/2] BCC: python: add a useful tool for mptcp

[Gang Yan]

On Mon, Apr 07, 2025 at 11:09:59AM +0200, Matthieu Baerts wrote:
Hi Matt,

> Hi Gang,
> 
> On 07/04/2025 04:37, Gang Yan wrote:
> > Multipath TCP (MPTCP) is an extension of the standard TCP protocol
> > that allows a single transport connection to use multiple network
> > interfaces. MPTCP is useful for applications like bandwidth
> > aggregation, failover, and more resilient connections.
> > 
> > Linux kernel starts to support MPTCP since v5.6, this patch provides
> > a method which can easily force applications use MPTCP socket without
> > modifing its code.
> > 
> > Signed-off-by: Gang Yan <yangang@kylinos.cn>
> > ---
> >  tools/mptcpboost.py  | 82 ++++++++++++++++++++++++++++++++++++++++++++
> >  tools/mptcpboost.txt | 22 ++++++++++++
> 
> Small detail: what about re-using the "mptcpify" name
>
OK, I'll use this name in v2.

> https://elixir.bootlin.com/linux/latest/source/tools/testing/selftests/bpf/progs/mptcpify.c
> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=ddba122428a7
> 
> Once applied on BCC side, we could update our website to point to this
> program:
> 
>   https://www.mptcp.dev/setup.html#force-applications-to-use-mptcp
> 
> >  2 files changed, 104 insertions(+)
> >  create mode 100644 tools/mptcpboost.py
> >  create mode 100644 tools/mptcpboost.txt
> > 
> > diff --git a/tools/mptcpboost.py b/tools/mptcpboost.py
> > new file mode 100644
> > index 00000000..0ddd731a
> > --- /dev/null
> > +++ b/tools/mptcpboost.py
> > @@ -0,0 +1,82 @@
> > +#!/usr/bin/env python
> > +#
> > +# mptcpboost Make the applications to use MPTCP.
> > +#           For Linux, uses BCC, eBPF. Embedded C.
> > +#
> > +# USAGE: mptcpboost -t
> > +#
> > +# Copyright 2025 Kylin Software, Inc.
> > +# Licensed under the Apache License, Version 2.0 (the "License")
> > +#
> > +# 05-Apr-2025   Gang Yan   Created this.
> > +
> > +import ctypes as ct
> > +import argparse
> > +import signal
> > +import time
> > +
> > +from bcc import BPF
> > +
> > +#arguments
> > +parser = argparse.ArgumentParser(
> > +         description="mptcpboost try to force applications use MPTCP")
> 
> detail: 'to' missing: try to force applications *to* use MPTCP
> 
> Maybe clearer if we add 'instead of TCP'?

Thanks for your suggestion, it sounds good.

> > +parser.add_argument("-t", "--targets", required=True, type=str,
> > +                    help="use ',' for multi targets, eg: 'iperf3,rsync'")
> 
> Could it be eventually optional to force all apps from the same CGroup
> to use MPTCP instead of TCP?
> 
> 
> Another idea is to restrict this transformation to the app passed in
> argument, e.g.
> 
>   mptcpify -- iperf3 -s
> 
> (but can be done later if this makes sense)

Yeah, I think this can be done later.

> > +
> > +args_str = parser.parse_args()
> > +args_list = [t.strip() for t in args_str.targets.split(',')]
> > +
> > +if (not BPF.support_fmod_ret()):
> > +    print("Your kernel version is too old,"
> > +          " fmod_ret method is only support kernel v5.6 and later.")
> 
> v5.7?
> 
> > +    exit()
> > +
> > +TASK_COMM_LEN = 18
> > +
> > +class app_name(ct.Structure):
> > +    _fields_ = [("str", ct.c_char * TASK_COMM_LEN)]
> > +
> > +# define BPF program
> > +prog = """
> > +#include <linux/net.h>
> > +#include <uapi/linux/in.h>
> > +#include <linux/string.h>
> > +
> > +struct app_name {
> > +    char name[TASK_COMM_LEN];
> > +};
> > +
> > +BPF_HASH(support_apps, struct app_name);
> > +
> > +KMOD_RET(update_socket_protocol, int family, int type, int protocol, int ret)
> > +{
> > +    struct app_name target = {};
> > +    bpf_get_current_comm(&target.name, TASK_COMM_LEN);
> > +
> > +    if ((family == AF_INET || family == AF_INET6) &&
> > +        type == SOCK_STREAM &&
> > +        (!protocol || protocol ==IPPROTO_TCP) &&
> 
> detail: space missing after '=='

Thanks!

> > +        support_apps.lookup(&target))
> > +        return IPPROTO_MPTCP;
> > +
> > +    return protocol;
> > +
> > +}
> > +
> > +"""
> > +
> > +b = BPF(text=prog)
> > +b.attach_fmod_ret("update_socket_protocol")
> > +
> > +support_apps = b.get_table("support_apps")
> > +for i in args_list:
> > +    app = i.encode()
> > +    name = app_name()
> > +    name.str = app[:TASK_COMM_LEN-1].ljust(TASK_COMM_LEN, b'\0')
> > +    support_apps[name] = ct.c_uint32(1)
> > +
> > +print("MPTCP is been applied in ", args_list);
> 
> detail: MPTCP is being forced for:
> 

OK!

> > +signal.pause()
> > +#while(1):
> > +#   time.sleep(200)
> 
> I guess you can remove the comments.

Sure, that's my fault.
> 
> Cheers,
> Matt
> -- 
> Sponsored by the NGI0 Core fund.
> 
> 

Re: [PATCH 0/2] BCC: python: support fmod_ret

[Matthieu Baerts]

Hi Gang,

On 07/04/2025 04:37, Gang Yan wrote:
> Support fmod_ret, and add a useful tool for mptcp, also
> the interface can be verified with this function.
> 
> Gang Yan (2):
>   BCC: Python: Support 'fmod_ret' method for eBPF
>   BCC: python: add a useful tool for mptcp

Thank you for looking at this!

Personally, I don't know how BCC is working internally, but the
modifications seem to make sense.

I have a few comments, but apart from that, feel free to create the PR
on BCC repo.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.

Re: [PATCH 0/2] BCC: python: support fmod_ret

[Gang Yan]

On Mon, Apr 07, 2025 at 11:07:04AM +0200, Matthieu Baerts wrote:
Hi Matt,
> Hi Gang,
> 
> On 07/04/2025 04:37, Gang Yan wrote:
> > Support fmod_ret, and add a useful tool for mptcp, also
> > the interface can be verified with this function.
> > 
> > Gang Yan (2):
> >   BCC: Python: Support 'fmod_ret' method for eBPF
> >   BCC: python: add a useful tool for mptcp
> 
> Thank you for looking at this!
> 
> Personally, I don't know how BCC is working internally, but the
> modifications seem to make sense.
> 
> I have a few comments, but apart from that, feel free to create the PR
> on BCC repo.
>

Thanks for the comments!

Can I add your <Reviewd-by> in this PR?

> Cheers,
> Matt
> -- 
> Sponsored by the NGI0 Core fund.
> 
> 

Re: [PATCH 0/2] BCC: python: support fmod_ret

[Matthieu Baerts]

Hi Gang,

On 08/04/2025 04:02, Gang Yan wrote:
> On Mon, Apr 07, 2025 at 11:07:04AM +0200, Matthieu Baerts wrote:
> Hi Matt,
>> Hi Gang,
>>
>> On 07/04/2025 04:37, Gang Yan wrote:
>>> Support fmod_ret, and add a useful tool for mptcp, also
>>> the interface can be verified with this function.
>>>
>>> Gang Yan (2):
>>>   BCC: Python: Support 'fmod_ret' method for eBPF
>>>   BCC: python: add a useful tool for mptcp
>>
>> Thank you for looking at this!
>>
>> Personally, I don't know how BCC is working internally, but the
>> modifications seem to make sense.
>>
>> I have a few comments, but apart from that, feel free to create the PR
>> on BCC repo.
>>
> 
> Thanks for the comments!
> 
> Can I add your <Reviewd-by> in this PR?

I don't think they use these tags in BCC. (If any, it should be more
Acked-by). Maybe better to add something like that in the Pull Request
message:

  @matttbe from the MPTCP kernel team had a look at the new tool.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.