Hi, bad checksum may be caused by the virtual network adapter that does not perform hardware checksum. I had this issue on a kvm test setup.
MTU is to be looked at, as udp does not handle very well packet fragmentation ( to say the least ). Could you reproduce the same issue using an openvpn tcp virtual link between your two servers ? Le 12/02/2015 12:23, Andrey Utkin a écrit : > We experience strange networking issue, not exactly specific to > kamailio, but still related to it. > Rtpengine's "ng" interface uses UDP. Protocol messages contains SDP, > and for encrypted video call those messages exceed 1500 bytes. > Everything works fine within localhost, but when rtpengine and > Kamailio are on different hosts, and when hosts are Amazon-hosted, we > have trouble. > > This is experienced with l3.large, t2.micro with Ubuntu 14. I believe > we don't have any special settings over system defaults. > We send a large datagram from remote host, e.g. with such trivial app in > python: > > import socket > UDP_IP = "123.123.123.123" # remote host IP > UDP_PORT = 33333 > MESSAGE = """ > .....0010......0020......0030......0040......0050......0060......0070......0080......0090......0100 > .....0110......0120......0130......0140......0150......0160......0170......0180......0190......0200 > .....0210......0220......0230......0240......0250......0260......0270......0280......0290......0300 > .....0310......0320......0330......0340......0350......0360......0370......0380......0390......0400 > .....0410......0420......0430......0440......0450......0460......0470......0480......0490......0500 > .....0510......0520......0530......0540......0550......0560......0570......0580......0590......0600 > .....0610......0620......0630......0640......0650......0660......0670......0680......0690......0700 > .....0710......0720......0730......0740......0750......0760......0770......0780......0790......0800 > .....0810......0820......0830......0840......0850......0860......0870......0880......0890......0900 > .....0910......0920......0930......0940......0950......0960......0970......0980......0990......1000 > .....1010......1020......1030......1040......1050......1060......1070......1080......1090......1100 > .....1110......1120......1130......1140......1150......1160......1170......1180......1190......1200 > .....1210......1220......1230......1240......1250......1260......1270......1280......1290......1300 > .....1310......1320......1330......1340......1350......1360......1370......1380......1390......1400 > .....1410......1420......1430......1440......1450......1460......1470......1480......1490......1500 > .....1510......1520......1530......1540......1550......1560......1570......1580......1590......1600 > .....1610......1620......1630......1640......1650......1660......1670......1680......1690......1700 > .....1710......1720......1730......1740......1750......1760......1770......1780......1790......1800 > .....1810......1820......1830......1840......1850......1860......1870......1880......1890......1900 > .....1910......1920......1930......1940......1950......1960......1970......1980......1990......2000""" > print "UDP target IP:", UDP_IP > print "UDP target port:", UDP_PORT > print "message:", MESSAGE > sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) > sock.sendto(MESSAGE, (UDP_IP, UDP_PORT)) > > Then we listen on that port with such trivial python app: > > import socket > UDP_IP = "172.31.4.102" # local ip > UDP_PORT = 33333 > sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) > sock.bind((UDP_IP, UDP_PORT)) > while True: > data, addr = sock.recvfrom(0x10000) > print "received message:", data > > > Meanwhile, we monitor the traffic with e.g. ngrep: > ngrep -t -e -d any -W byline -O large_udp.pcap port 33333 or > '(ip[6:2]' '&' '0x1fff)' '!=' '0' > (the part after "or" catches segments of segmented packets) > About the host: > # uname -a > Linux hostname 3.16.0-30-generic #40~14.04.1-Ubuntu SMP Thu Jan 15 > 17:43:14 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux > Also linux-image-3.13.0-36-generic and linux-image-3.13.0-45-generic > behave in same way. > > What we see: > - ngrep shows the packets with correct contents. All segments are delivered. > - application doesn't get any data at all > > Rarely dmesg shows such messages: > [ 102.161679] UDP: bad checksum. From 123.123.123.124:56439 to > 172.31.4.102:33333 ulen 2008 > but it is logged really rarely, so this is surely not what happens on > every packet transmission. > This test works fine on e.g. cheapest DigitalOcean VPS. > I am concerned with this issue because rtpengine software has UDP > interface. So on Amazon hosts this interface works only within > localhost, and I cannot distribute software to different nodes. > > Any thoughts? What's wrong, how to fix? > > >
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