[Serusers] append_hf_helper brings strange characters.

[szj]

  I use the SER 0.10.99 version. I want to modify
the procedure of tm module. Before sending the request
and forwarding the reply, I managed to modify the
request and response, f.e, to insert another header
into the request and response. In the request, it
works correctly.But in the response, sometime it
works, sometimes it failed. The debug log is as
follows.

 2(2196)  old size: 784, new size: 869
 2(2196) build_res_from_sip_res: copied size: orig:76, new: 161, rest: 
708 msg=
SIP/2.0 200 OK^M
 >P-Security-Nobody:Zgrrv1Y/19zYJGyKXm4obgHZZP5jY59qxbhLxEUgZO11uI41w1QzJKqSbjYQ6G7e/ViClnetse/aCE+dj/TbAZFQa45dL/wPzAS4MDKABos=^M
 >/QjFhTWNKQaL8k=^M/*<90>*Via: SIP/2.0/UDP 
192.168.0.19:5500;branch=z9hG4bK1648283653^M
Record-Route: <sip:192.168.0.19;ftag=549451184;lr>^M
From: <sip:861111 at sip.suntest.com>;tag=81929894;tag=549451184^M
To: <sip:862222 at sip.suntest.com>;tag=882426148^M
Call-ID: 903055665 at 192.168.0.19^M
CSeq: 21 INVITE^M
Contact: <sip:862222 at 192.168.0.19:6600>^M
Allow: INVITE, ACK, OPTIONS, CANCEL, BYE, SUBSCRIBE, NOTIFY, MESSAGE, INFO^M
Content-Type: application/sdp^M
Content-Length:   261^M
^M
v=0^M
o=nobody 20041028 20000001 IN IP4 192.168.0.19^M
s=A call^M
c=IN IP4 192.168.0.19^M
t=1111396796 1111400396^M
m=audio 7100 RTP/AVP 0 8^M
a=rtpmap:0 PCMU/8000^M
a=rtpmap:8 PCMA/8000^M
m=video 7600 RTP/AVP 98 31^M
a=rtpmap:98 H263/90000^M
a=rtpmap:31 vf=4/CIF/1/768^M

  I insert the header "P-Security-Nobody: " into the
response using the modified version of function
"append_hf_helper". There are some strange code in
the backend of inserted header. f.e, the italic black
characters in the log. I had added a null terminator
at the tail of the inserted header.

  I guess it is caused by the data_lump functions.
  Who can tell me the real reason of that?

  Thanks for your kind help.
  Best Regards.

Sun Zongjun