Hello, On Mon, 17 Jul 2017, 李春 wrote: > I have meet a very strange problem in my LVS environment. > > > when I connect to mysqld real server, mysql client is ok. > when I connect to LVS to access to the real server, mysql client report error. > > > I config the LVS as DR mode like this: > ``` > ipvsadm -A -t 158.222.165.185:3306 -s wrr > ipvsadm -a -t 158.222.165.185:3306 -r 158.222.165.125:3306 -g -w 100 > ``` > > > > And I have tcpdump the package on the LVS and real server. > Sync/Sync+ack/ack of Three-way Handshake is ok，and four-way handshake is ok. > But when mysql client send the login request (user/password) package, > the package fragment. > > > As show as follows,The LVS received the package and send it the real > server correct(length 252). > But real server get a fragment of the package (length 248) and a error > chksum. It have missed the 4 bytes fragment of the package. > > > Here is the package I have ```tcpdump -lnnneeevvv``` on the LVS. > * 9c:dc:71:4d:49:d0 = 158.222.165.126 is the client > * 24:8a:07:64:7f:21 = 158.222.165.185 is the VIP and the director > * 24:8a:07:64:56:41 = 158.222.165.185 is the real server > > > LVS package: > ``` > 19:12:22.229356 9c:dc:71:4d:49:d0 > 24:8a:07:64:7f:21, ethertype IPv4 > (0x0800), length 252: (tos 0x8, ttl 64, id 56669, offset 0, flags > [DF], proto TCP (6), l > 158.222.165.126.37691 > 158.222.165.185.3306: Flags [P.], cksum > 0x5d97 (correct), seq 0:198, ack 83, win 115, length 198 > 19:12:22.229367 24:8a:07:64:7f:21 > 24:8a:07:64:56:41, ethertype IPv4 > (0x0800), length 252: (tos 0x8, ttl 64, id 56669, offset 0, flags > [DF], proto TCP (6), l > 158.222.165.126.37691 > 158.222.165.185.3306: Flags [P.], cksum > 0x5d97 (correct), seq 0:198, ack 83, win 115, length 198 > ``` > > > real server packages: > ``` > 19:12:21.803118 24:8a:07:64:7f:21 > 24:8a:07:64:56:41, ethertype IPv4 > (0x0800), length 248: (tos 0x8, ttl 64, id 56668, offset 0, flags > [DF], proto TCP (6), l > 158.222.165.126.37691 > 158.222.165.185.3306: Flags [.], cksum > 0x5d97 (incorrect -> 0x4883), seq 1:195, ack 83, win 115, length 194 > 19:12:21.803126 24:8a:07:64:7f:21 > 24:8a:07:64:56:41, ethertype IPv4 > (0x0800), length 60: (tos 0x8, ttl 64, id 56669, offset 0, flags [DF], > proto TCP (6), le > 158.222.165.126.37691 > 158.222.165.185.3306: Flags [P.], cksum > 0x7973 (incorrect -> 0x5fb3), seq 199, ack 83, win 115, length 0 > ``` > > > > * we run the test on rhel6.7 with ipvsadm v1.26 2008/5/15 (compiled > with popt and IPVS v1.2.1) > * our network engineer have mirror the port of LVS and report that the > package is fragmented from LVS director. > * we have replace the broadcom network card to mellanox netword card, > but it still the same problem > > > And I have not config net.ipv4.ip_forward = 1 accord to > http://www.austintek.com/LVS/LVS-HOWTO/HOWTO/LVS-HOWTO.LVS-DR.html > But if I config "net.ipv4.ip_forward = 1 ", there are no package > fragment. MySQL connect to mysqld (throught LVS) successfully. > > > Have any one meet the problem, do you resolve it ? Or any one can help > to fix it. There can be a problem with fragments but your tcpdump output does not show such fragments, even in previous emails. According to 'man tcpdump': Fragmented Internet datagrams are printed as (frag id:size@offset+) (frag id:size@offset) What exactly is the kernel version (uname -a) ? You can use such minimum options: tcpdump -s0 -lennn -vvv ... Regards -- Julian Anastasov <ja@xxxxxx>
