That is interesting. Can you check whether you are using hardware checksum
offloading?
Install 'ethtool' and run:
ethtool --show-offload eth0
On Mon, Sep 23, 2013 at 5:37 PM, jonsm...@gmail.com <jonsm...@gmail.com>wrote:
> I used
> tcpdump -n -v -e -i eth0
>
> So what is causing those incorrect checksums?
>
> 192.168.1.40 > 224.0.0.22: igmp v3 report, 3 group record(s)
> [gaddr 224.0.0.251 is_ex { }] [gaddr 239.192.83.80 is_ex { }] [gaddr
> 239.255.255.250 is_ex { }]
> 02:35:41.227580 00:1f:90:7e:af:3d > 01:80:c2:00:00:00, 802.3, length
> 60: LLC, dsap STP (0x42) Individual, ssap STP (0x42) Command, ctrl
> 0x03: STP 802.1d, Config, Flags [none], bridge-id
> 8000.00:18:01:f9:89:66.8004, length 43
> message-age 0.00s, max-age 20.00s, hello-time 2.00s, forwarding-delay
> 15.00s
> root-id 8000.00:18:01:f9:89:66, root-pathcost 0
> 02:35:41.238900 70:71:bc:b8:9b:ee > ff:ff:ff:ff:ff:ff, ethertype ARP
> (0x0806), length 60: Ethernet (len 6), IPv4 (len 4), Request who-has
> 192.168.1.85 tell 192.168.1.40, length 46
> 02:35:41.239060 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype ARP
> (0x0806), length 42: Ethernet (len 6), IPv4 (len 4), Reply
> 192.168.1.85 is-at 00:0a:52:00:00:02, length 28
> 02:35:41.239260 70:71:bc:b8:9b:ee > 00:0a:52:00:00:02, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 24793, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.40.55361 > 192.168.1.85.80: Flags [S], cksum 0xd005
> (correct), seq 1922975579, win 14600, options [mss 1460,sackOK,TS val
> 18294658 ecr 0,nop,wscale 7], length 0
> 02:35:41.239800 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55361: Flags [S.], cksum 0x83fc
> (incorrect -> 0x488a), seq 2923783498, ack 1922975580, win 14480,
> options [mss 1460,sackOK,TS val 29783 ecr 18294658,nop,wscale 2],
> length 0
> 02:35:41.490020 70:71:bc:b8:9b:ee > 00:0a:52:00:00:02, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 62082, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.40.55362 > 192.168.1.85.80: Flags [S], cksum 0x0b17
> (correct), seq 2841957699, win 14600, options [mss 1460,sackOK,TS val
> 18294721 ecr 0,nop,wscale 7], length 0
> 02:35:41.490540 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55362: Flags [S.], cksum 0x83fc
> (incorrect -> 0x7202), seq 3561640133, ack 2841957700, win 14480,
> options [mss 1460,sackOK,TS val 29808 ecr 18294721,nop,wscale 2],
> length 0
> 02:35:42.237600 70:71:bc:b8:9b:ee > 00:0a:52:00:00:02, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 24794, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.40.55361 > 192.168.1.85.80: Flags [S], cksum 0xcf0b
> (correct), seq 1922975579, win 14600, options [mss 1460,sackOK,TS val
> 18294908 ecr 0,nop,wscale 7], length 0
> 02:35:42.237980 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55361: Flags [S.], cksum 0x83fc
> (incorrect -> 0x4843), seq 2923783498, ack 1922975580, win 14480,
> options [mss 1460,sackOK,TS val 29854 ecr 18294658,nop,wscale 2],
> length 0
> 02:35:42.489760 70:71:bc:b8:9b:ee > 00:0a:52:00:00:02, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 62083, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.40.55362 > 192.168.1.85.80: Flags [S], cksum 0x0a1d
> (correct), seq 2841957699, win 14600, options [mss 1460,sackOK,TS val
> 18294971 ecr 0,nop,wscale 7], length 0
> 02:35:42.490140 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55362: Flags [S.], cksum 0x83fc
> (incorrect -> 0x719e), seq 3561640133, ack 2841957700, win 14480,
> options [mss 1460,sackOK,TS val 29908 ecr 18294721,nop,wscale 2],
> length 0
> 02:35:42.943020 00:18:dd:31:3b:41 > 01:00:5e:00:00:01, ethertype IPv4
> (0x0800), length 60: (tos 0x0, ttl 1, id 0, offset 0, flags [none],
> proto IGMP (2), length 28)
> 192.168.1.64 > 224.0.0.1: igmp v2 report 224.0.0.1
> 02:35:42.943240 00:18:dd:31:3b:41 > 01:00:5e:00:00:01, ethertype IPv4
> (0x0800), length 60: (tos 0x0, ttl 1, id 0, offset 0, flags [none],
> proto IGMP (2), length 28)
> 169.254.91.114 > 224.0.0.1: igmp v2 report 224.0.0.1
> 02:35:43.228180 00:1f:90:7e:af:3d > 01:80:c2:00:00:00, 802.3, length
> 60: LLC, dsap STP (0x42) Individual, ssap STP (0x42) Command, ctrl
> 0x03: STP 802.1d, Config, Flags [none], bridge-id
> 8000.00:18:01:f9:89:66.8004, length 43
> message-age 0.00s, max-age 20.00s, hello-time 2.00s, forwarding-delay
> 15.00s
> root-id 8000.00:18:01:f9:89:66, root-pathcost 0
> 02:35:43.567260 00:23:ee:3d:84:e3 > ff:ff:ff:ff:ff:ff, ethertype IPv4
> (0x0800), length 60: (tos 0x0, ttl 64, id 18534, offset 0, flags
> [none], proto UDP (17), length 40)
> 169.254.1.250.53586 > 169.254.1.255.5000: [udp sum ok] UDP, length 12
> 02:35:43.580920 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55362: Flags [S.], cksum 0x83fc
> (incorrect -> 0x7131), seq 3561640133, ack 2841957700, win 14480,
> options [mss 1460,sackOK,TS val 30017 ecr 18294721,nop,wscale 2],
> length 0
> 02:35:43.581140 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55361: Flags [S.], cksum 0x83fc
> (incorrect -> 0x47a0), seq 2923783498, ack 1922975580, win 14480,
> options [mss 1460,sackOK,TS val 30017 ecr 18294658,nop,wscale 2],
> length 0
> 02:35:44.242200 70:71:bc:b8:9b:ee > 00:0a:52:00:00:02, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 24795, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.40.55361 > 192.168.1.85.80: Flags [S], cksum 0xcd16
> (correct), seq 1922975579, win 14600, options [mss 1460,sackOK,TS val
> 18295409 ecr 0,nop,wscale 7], length 0
> 02:35:44.242580 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55361: Flags [S.], cksum 0x83fc
> (incorrect -> 0x475e), seq 2923783498, ack 1922975580, win 14480,
> options [mss 1460,sackOK,TS val 30083 ecr 18294658,nop,wscale 2],
> length 0
> 02:35:44.494240 70:71:bc:b8:9b:ee > 00:0a:52:00:00:02, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 62084, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.40.55362 > 192.168.1.85.80: Flags [S], cksum 0x0828
> (correct), seq 2841957699, win 14600, options [mss 1460,sackOK,TS val
> 18295472 ecr 0,nop,wscale 7], length 0
> 02:35:44.494620 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55362: Flags [S.], cksum 0x83fc
> (incorrect -> 0x70d6), seq 3561640133, ack 2841957700, win 14480,
> options [mss 1460,sackOK,TS val 30108 ecr 18294721,nop,wscale 2],
> length 0
> 02:35:44.823460 68:7f:74:0a:fb:ec > 33:33:00:00:00:01, ethertype IPv6
> (0x86dd), length 118: (hlim 255, next-header ICMPv6 (58) payload
> length: 64) fe80::6a7f:74ff:fe0a:fbec > ff02::1: [icmp6 sum ok] ICMP6,
> router advertisement, length 64
> hop limit 64, Flags [none], pref medium, router lifetime 30s,
> reachable time 0s, retrans time 0s
> prefix info option (3), length 32 (4): 2002:ad4c:16cc:1::/64, Flags
> [onlink, auto, router], valid time 86400s, pref. time 86400s
> 0x0000: 40e0 0001 5180 0001 5180 0000 0000 2002
> 0x0010: ad4c 16cc 0001 0000 0000 0000 0000
> mtu option (5), length 8 (1): 1280
> 0x0000: 0000 0000 0500
> source link-address option (1), length 8 (1): 68:7f:74:0a:fb:ec
> 0x0000: 687f 740a fbec
> 02:35:45.176120 00:24:a0:0d:07:ac > ff:ff:ff:ff:ff:ff, ethertype IPv4
> (0x0800), length 60: (tos 0x0, ttl 64, id 18504, offset 0, flags
> [none], proto UDP (17), length 40)
> 169.254.1.159.59527 > 169.254.1.255.5000: [udp sum ok] UDP, length 12
> 02:35:45.180740 00:24:a0:0d:07:8d > ff:ff:ff:ff:ff:ff, ethertype IPv4
> (0x0800), length 60: (tos 0x0, ttl 64, id 18533, offset 0, flags
> [none], proto UDP (17), length 40)
> 169.254.1.139.46505 > 169.254.1.255.5000: [udp sum ok] UDP, length 12
> 02:35:45.228760 00:1f:90:7e:af:3d > 01:80:c2:00:00:00, 802.3, length
> 60: LLC, dsap STP (0x42) Individual, ssap STP (0x42) Command, ctrl
> 0x03: STP 802.1d, Config, Flags [none], bridge-id
> 8000.00:18:01:f9:89:66.8004, length 43
> message-age 0.00s, max-age 20.00s, hello-time 2.00s, forwarding-delay
> 15.00s
> root-id 8000.00:18:01:f9:89:66, root-pathcost 0
>
>
> 02:39:22.757460 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55390: Flags [S.], cksum 0x83fc
> (incorrect -> 0x09e7), seq 847126340, ack 4019952613, win 14480,
> options [mss 1460,sackOK,TS val 51935 ecr 18350022,nop,wscale 2],
> length 0
> 0x0000: 4500 003c 0000 4000 4006 b6ee c0a8 0155
> 0x0010: c0a8 0128 0050 d85e 327e 1f44 ef9b 9be5
> 0x0020: a012 3890 83fc 0000 0204 05b4 0402 080a
> 0x0030: 0000 cadf 0117 ffc6 0103 0302
>
> 02:39:23.504240 00:0a:52:00:00:02 > 70:71:bc:b8:9b:ee, ethertype IPv4
> (0x0800), length 74: (tos 0x0, ttl 64, id 0, offset 0, flags [DF],
> proto TCP (6), length 60)
> 192.168.1.85.80 > 192.168.1.40.55389: Flags [S.], cksum 0x83fc
> (incorrect -> 0x3216), seq 2653743405, ack 1971632174, win 14480,
> options [mss 1460,sackOK,TS val 52006 ecr 18349959,nop,wscale 2],
> length 0
> 0x0000: 4500 003c 0000 4000 4006 b6ee c0a8 0155
> 0x0010: c0a8 0128 0050 d85d 9e2c e92d 7584 b82e
> 0x0020: a012 3890 83fc 0000 0204 05b4 0402 080a
> 0x0030: 0000 cb26 0117 ff87 0103 0302
>
>
>
> --
> Jon Smirl
> jonsm...@gmail.com
> _______________________________________________
> openwrt-devel mailing list
> openwrt-devel@lists.openwrt.org
> https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel
>
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