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Feature #6115

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modem: MTU not set properly on tun iface

Added by pespin 7 months ago. Updated 2 months ago.

Status:
Feedback
Priority:
Normal
Assignee:
Category:
OsmocomBB modem (host)
Target version:
Start date:
07/26/2023
Due date:
% Done:

0%

Resolution:
Spec Reference:
Tags:

Description

tested using iperf3 client in the netns + tun created by the "modem" app, against an iperf3 server running in the IP address of the GGSN outside the netns:

iperf3 -c 176.16.222.1 -u -V
iperf3 -s -B 176.16.222.1

The iperf3 tries to fill in the MTU when sending packets, but there seems to be a problem when enqueueing them:

20230726174215423 DLLC ERROR llc.c:359 LLE(c34b1498/c914945e,SNDCP3){ASSIGNED_ADM} Cannot Tx 1480 bytes (N201-U=500)
20230726174215433 DTUN DEBUG app_modem.c:121 APN(internet): system wants to transmit IPv4 pkt to 176.16.222.1 (1476 bytes)
20230726174215433 DSNDCP INFO sndcp_prim.c:424 Rx from upper layers: SN-UNITDATA.request
20230726174215434 DSNDCP DEBUG sndcp.c:130 modem_sndcp_prim_down_cb(): Rx LL-UNITDATA.request TLLI=0xc914945e SAPI=SNDCP3 L3=[66 00 05 d5 45 00 05 c4 78 bc 40 00 40 11 a0 47 b0 10 de 02 b0 10 de 01 aa 53 14 51 05 b0 3b dd 00 00 2a ed 00 0a f5 b0 00 00 01 8c 21 52 df 52 61 ce 27 d9 5b ea e8 ec 6d fe 02 45 1b 9c cc dc ec 38 8f e5 29 e9 b0 a0 1c 01 2b 3b 39 e1 9c 51 2f c5 79 14 de c8 b6 13 23 c5 b1 ff 79 d0 5e 1b 04 b2 4e 3f 90 a3 3a 00 df 13 ab 43 8c b7 d3 a8 45 39 a2 70 06 76 c1 fe 19 95 76 3a 74 51 18 6c 5c 4d c1 a0 4b 80 51 3d 73 c6 95 14 e3 76 f9 af 1c f4 28 70 0d 4e 78 21 83 32 a8 12 82 a6 76 01 f3 75 36 77 08 8d 0f 16 c7 be 7a 1b 51 bf 64 9b 0f fc c3 86 bd 1f 0a b0 8c 6f f7 d2 01 da 5b 07 72 72 66 4e 80 55 a6 77 86 bb 76 5c 9c 48 85 a3 5f 97 70 ce b0 ff 79 f9 e0 10 92 f3 e0 bc a0 ee d2 08 90 55 04 6c 8a 28 31 fb 00 66 24 54 67 36 c9 1d 0c 71 ff 09 52 7a 1b 4d 77 02 87 47 89 9f 62 ae da 4c 14 88 8b f5 cc 28 0a df 59 89 e2 72 64 28 dc 0e b2 59 10 57 ae 60 70 9c 31 ee 5d 55 c1 66 82 70 aa 4c 3b aa 79 45 8f e1 06 3c 68 66 8f 0b 86 90 4e 73 fd a9 f3 2e 9b 4a 3f 58 69 82 b1 c1 c2 4e af 5a dc d0 5b 6b 22 17 4f 74 8b 17 6e 0d 23 13 23 c2 1b f3 b0 56 ec fa 3b 48 98 bd 9b 7e e4 c9 a5 37 3f ed 05 d2 0e 0f f4 21 af 9e d0 83 31 70 12 8b 14 96 46 bf b9 3a 64 0a 75 da 0f 8d 83 d9 8a 9b 26 0b 4c 65 1d 26 f1 9e 75 08 8a 48 03 64 c0 a1 de d6 59 ad 9f 6b f6 cf 4a 65 08 cf 18 68 54 16 8f af 61 8c 06 fb 6a 09 93 c9 4a fb 00 94 16 9c 2f f3 a6 5e 90 55 29 7e 3a b9 04 2d 69 06 f7 89 2e 53 52 67 c4 73 43 05 9a ce af f9 7d 77 26 c1 a5 aa c8 8e 0f 80 c4 00 be 71 3f 1a f8 38 f1 4c 06 59 07 ac 06 32 eb 5a d2 35 db 3d 11 0c fa af 04 8c 56 d0 a8 3a 2f 50 9f cb 0d 44 10 38 f9 ab 79 97 0a 11 8a 21 4a d1 0d 4b 8c ea f4 79 2b ac f0 48 52 67 b8 36 05 1f 2e bb e4 c5 d1 8c 35 d4 8e fb 8d 8d 8d 15 26 fe 37 fd bb 6b af 2a b4 11 97 24 b0 28 15 ce 95 97 d5 7f 62 8b 73 77 d7 7f a6 72 23 35 fb 60 65 de 84 54 b9 a0 30 21 3e 87 f2 a7 9c 82 0c 92 6a 28 e4 06 6e 84 e9 6a 1c 20 5c 30 dd 1b 80 71 88 9f 5b 3b 74 2d 18 ed 6e f7 8c 67 ba ed 05 06 13 76 58 c0 7b 1b 1d d9 23 14 30 ef 97 4c 1d 48 a2 8e 83 49 1b 6b 75 90 b6 a0 98 e9 7d b1 c7 fa 39 6e a5 18 9a 94 ab 6d 18 d2 1f 61 39 a1 2e ca 7f b9 23 73 7d 29 a1 6a bd f6 9b e2 d9 cf fa 0f ca 46 c3 be 4a cc 7d 19 9e 23 be 74 65 7c cc e8 d7 f7 6c 8a 64 7b 0b 14 d3 b5 3f 19 47 94 08 70 23 02 01 2f 4d 09 07 4d 1f a6 6f b0 3b b3 7d 14 75 74 e5 1b 93 0a 52 0e 2a 02 e2 60 a9 dd 52 42 c9 c7 ee ab fb 7f fb 81 09 07 7a e7 64 1d bf 56 ad 68 c6 bc 73 81 a9 5a 03 4d 3f 02 66 73 87 01 11 dc f2 ab f9 a6 77 f2 db f3 4b 1f 32 05 4f ea 96 bc 7b e3 a5 e0 b4 de 3b ed 34 1f 95 9e ed f9 aa a6 ef 56 ea 17 a4 1a ad ea 64 8c f3 4b 05 a1 cd 31 92 82 c4 fa 43 07 f2 01 a4 9c e4 ae 4c cd ad f0 34 ec cb 4b 4d 3a b3 c1 3f b5 1f 0c 6a 8b d1 fb 2f 4e d6 59 c1 a3 61 1c cf 01 26 32 5b 97 a9 9a 31 16 b3 11 10 e6 ec 0f 74 d4 9e eb 57 ae 95 30 bc 8b 2f 41 fc fc 73 46 f8 1b 06 c6 b6 9c e7 a9 c3 13 2c 9d 93 f8 cc 61 d5 ff 09 4e 67 dc 79 60 80 67 00 86 83 d5 45 ad 5c f0 21 2b 81 29 98 19 85 cc 70 2c 43 0f bb 13 4d 31 41 5c 49 af d1 3d 82 fc 72 74 6b 81 a9 d4 d8 4a 75 8e 2c 54 f8 b1 1c 21 5e d6 f5 f8 0d 51 13 bc 6b 09 e9 d6 a0 bf 62 f8 b0 a7 64 39 fb 71 a1 b3 53 b9 c2 4c 9d 93 3a 78 9f 73 12 5f 3a f3 c7 73 73 20 bc 82 59 79 f2 b5 b7 13 43 0e 73 f7 fd 4a df 51 9b 44 78 e7 7f 18 5a a0 fb 88 94 e6 3a 27 23 bf e7 10 bb 50 6e 4d 59 a9 9c 83 ca 67 d7 60 92 99 e5 5e a4 86 42 7e 7b 3a b7 4b c0 4f 85 71 52 0c 42 35 30 46 e8 62 85 96 42 d8 77 5c 9a f8 ab 74 52 a8 17 03 cf 16 34 18 fb e1 85 00 83 e8 b1 83 0e 4f 43 25 40 b5 29 2c e1 c1 8f 61 0d a2 63 2e 41 06 97 66 1a a6 38 db f4 bc 0d 70 c7 af 53 cd e6 be 00 bc 2b df 2a 15 98 dc 05 30 cd 25 bd 0f 59 74 ba cd ba 2d 67 c3 69 c4 72 00 40 76 7e 0f d9 95 bc 25 34 e6 30 89 f6 fa 6e d4 10 98 2d 32 b5 91 2e 4a e6 01 0f e2 34 d5 0f 91 b6 cb 49 e1 d2 86 6c 9b d4 06 16 59 93 86 68 d5 01 0b 47 ac 4b 92 fa a1 5d f4 46 a4 bc 89 3b 06 54 be e4 77 b6 0d 89 47 9d 70 9b 97 9e 0b 04 03 88 96 1b 63 31 81 3d 6d da 86 c8 a6 af 43 31 1f 99 7f da fa b9 44 a2 6c 31 ff 1d 3d 41 67 78 9f bb e3 2b 8b 7c dc 20230726174215434 DLLC INFO llc_prim.c:157 Rx from upper layers: LL-UNITDATA.request
20230726174215434 DLLC ERROR llc.c:359 LLE(c34b1498/c914945e,SNDCP3){ASSIGNED_ADM} Cannot Tx 1480 bytes (N201-U=500)
20230726174215441 DRLCMAC INFO rlcmac.c:789 TS=6 FN=93231 Rx Pkt DL Dummy Ctrl Block
20230726174215444 DTUN DEBUG app_modem.c:121 APN(internet): system wants to transmit IPv4 pkt to 176.16.222.1 (1476 bytes)
20230726174215445 DSNDCP INFO sndcp_prim.c:424 Rx from upper layers: SN-UNITDATA.request
20230726174215445 DSNDCP DEBUG sndcp.c:130 modem_sndcp_prim_down_cb(): Rx LL-UNITDATA.request TLLI=0xc914945e SAPI=SNDCP3 L3=[66 00 05 d6 45 00 05 c4 78 bd 40 00 40 11 a0 46 b0 10 de 02 b0 10 de 01 aa 53 14 51 05 b0 10 db 00 00 2a ed 00 0b 20 b1 00 00 01 8d 21 52 df 52 61 ce 27 d9 5b ea e8 ec 6d fe 02 45 1b 9c cc dc ec 38 8f e5 29 e9 b0 a0 1c 01 2b 3b 39 e1 9c 51 2f c5 79 14 de c8 b6 13 23 c5 b1 ff 79 d0 5e 1b 04 b2 4e 3f 90 a3 3a 00 df 13 ab 43 8c b7 d3 a8 45 39 a2 70 06 76 c1 fe 19 95 76 3a 74 51 18 6c 5c 4d c1 a0 4b 80 51 3d 73 c6 95 14 e3 76 f9 af 1c f4 28 70 0d 4e 78 21 83 32 a8 12 82 a6 76 01 f3 75 36 77 08 8d 0f 16 c7 be 7a 1b 51 bf 64 9b 0f fc c3 86 bd 1f 0a b0 8c 6f f7 d2 01 da 5b 07 72 72 66 4e 80 55 a6 77 86 bb 76 5c 9c 48 85 a3 5f 97 70 ce b0 ff 79 f9 e0 10 92 f3 e0 bc a0 ee d2 08 90 55 04 6c 8a 28 31 fb 00 66 24 54 67 36 c9 1d 0c 71 ff 09 52 7a 1b 4d 77 02 87 47 89 9f 62 ae da 4c 14 88 8b f5 cc 28 0a df 59 89 e2 72 64 28 dc 0e b2 59 10 57 ae 60 70 9c 31 ee 5d 55 c1 66 82 70 aa 4c 3b aa 79 45 8f e1 06 3c 68 66 8f 0b 86 90 4e 73 fd a9 f3 2e 9b 4a 3f 58 69 82 b1 c1 c2 4e af 5a dc d0 5b 6b 22 17 4f 74 8b 17 6e 0d 23 13 23 c2 1b f3 b0 56 ec fa 3b 48 98 bd 9b 7e e4 c9 a5 37 3f ed 05 d2 0e 0f f4 21 af 9e d0 83 31 70 12 8b 14 96 46 bf b9 3a 64 0a 75 da 0f 8d 83 d9 8a 9b 26 0b 4c 65 1d 26 f1 9e 75 08 8a 48 03 64 c0 a1 de d6 59 ad 9f 6b f6 cf 4a 65 08 cf 18 68 54 16 8f af 61 8c 06 fb 6a 09 93 c9 4a fb 00 94 16 9c 2f f3 a6 5e 90 55 29 7e 3a b9 04 2d 69 06 f7 89 2e 53 52 67 c4 73 43 05 9a ce af f9 7d 77 26 c1 a5 aa c8 8e 0f 80 c4 00 be 71 3f 1a f8 38 f1 4c 06 59 07 ac 06 32 eb 5a d2 35 db 3d 11 0c fa af 04 8c 56 d0 a8 3a 2f 50 9f cb 0d 44 10 38 f9 ab 79 97 0a 11 8a 21 4a d1 0d 4b 8c ea f4 79 2b ac f0 48 52 67 b8 36 05 1f 2e bb e4 c5 d1 8c 35 d4 8e fb 8d 8d 8d 15 26 fe 37 fd bb 6b af 2a b4 11 97 24 b0 28 15 ce 95 97 d5 7f 62 8b 73 77 d7 7f a6 72 23 35 fb 60 65 de 84 54 b9 a0 30 21 3e 87 f2 a7 9c 82 0c 92 6a 28 e4 06 6e 84 e9 6a 1c 20 5c 30 dd 1b 80 71 88 9f 5b 3b 74 2d 18 ed 6e f7 8c 67 ba ed 05 06 13 76 58 c0 7b 1b 1d d9 23 14 30 ef 97 4c 1d 48 a2 8e 83 49 1b 6b 75 90 b6 a0 98 e9 7d b1 c7 fa 39 6e a5 18 9a 94 ab 6d 18 d2 1f 61 39 a1 2e ca 7f b9 23 73 7d 29 a1 6a bd f6 9b e2 d9 cf fa 0f ca 46 c3 be 4a cc 7d 19 9e 23 be 74 65 7c cc e8 d7 f7 6c 8a 64 7b 0b 14 d3 b5 3f 19 47 94 08 70 23 02 01 2f 4d 09 07 4d 1f a6 6f b0 3b b3 7d 14 75 74 e5 1b 93 0a 52 0e 2a 02 e2 60 a9 dd 52 42 c9 c7 ee ab fb 7f fb 81 09 07 7a e7 64 1d bf 56 ad 68 c6 bc 73 81 a9 5a 03 4d 3f 02 66 73 87 01 11 dc f2 ab f9 a6 77 f2 db f3 4b 1f 32 05 4f ea 96 bc 7b e3 a5 e0 b4 de 3b ed 34 1f 95 9e ed f9 aa a6 ef 56 ea 17 a4 1a ad ea 64 8c f3 4b 05 a1 cd 31 92 82 c4 fa 43 07 f2 01 a4 9c e4 ae 4c cd ad f0 34 ec cb 4b 4d 3a b3 c1 3f b5 1f 0c 6a 8b d1 fb 2f 4e d6 59 c1 a3 61 1c cf 01 26 32 5b 97 a9 9a 31 16 b3 11 10 e6 ec 0f 74 d4 9e eb 57 ae 95 30 bc 8b 2f 41 fc fc 73 46 f8 1b 06 c6 b6 9c e7 a9 c3 13 2c 9d 93 f8 cc 61 d5 ff 09 4e 67 dc 79 60 80 67 00 86 83 d5 45 ad 5c f0 21 2b 81 29 98 19 85 cc 70 2c 43 0f bb 13 4d 31 41 5c 49 af d1 3d 82 fc 72 74 6b 81 a9 d4 d8 4a 75 8e 2c 54 f8 b1 1c 21 5e d6 f5 f8 0d 51 13 bc 6b 09 e9 d6 a0 bf 62 f8 b0 a7 64 39 fb 71 a1 b3 53 b9 c2 4c 9d 93 3a 78 9f 73 12 5f 3a f3 c7 73 73 20 bc 82 59 79 f2 b5 b7 13 43 0e 73 f7 fd 4a df 51 9b 44 78 e7 7f 18 5a a0 fb 88 94 e6 3a 27 23 bf e7 10 bb 50 6e 4d 59 a9 9c 83 ca 67 d7 60 92 99 e5 5e a4 86 42 7e 7b 3a b7 4b c0 4f 85 71 52 0c 42 35 30 46 e8 62 85 96 42 d8 77 5c 9a f8 ab 74 52 a8 17 03 cf 16 34 18 fb e1 85 00 83 e8 b1 83 0e 4f 43 25 40 b5 29 2c e1 c1 8f 61 0d a2 63 2e 41 06 97 66 1a a6 38 db f4 bc 0d 70 c7 af 53 cd e6 be 00 bc 2b df 2a 15 98 dc 05 30 cd 25 bd 0f 59 74 ba cd ba 2d 67 c3 69 c4 72 00 40 76 7e 0f d9 95 bc 25 34 e6 30 89 f6 fa 6e d4 10 98 2d 32 b5 91 2e 4a e6 01 0f e2 34 d5 0f 91 b6 cb 49 e1 d2 86 6c 9b d4 06 16 59 93 86 68 d5 01 0b 47 ac 4b 92 fa a1 5d f4 46 a4 bc 89 3b 06 54 be e4 77 b6 0d 89 47 9d 70 9b 97 9e 0b 04 03 88 96 1b 63 31 81 3d 6d da 86 c8 a6 af 43 31 1f 99 7f da fa b9 44 a2 6c 31 ff 1d 3d 41 67 78 9f bb e3 2b 8b 7c dc 20230726174215445 DLLC INFO llc_prim.c:157 Rx from upper layers: LL-UNITDATA.request
20230726174215445 DLLC ERROR llc.c:359 LLE(c34b1498/c914945e,SNDCP3){ASSIGNED_ADM} Cannot Tx 1480 bytes (N201-U=500)
20230726174215453 DTUN DEBUG app_modem.c:121 APN(internet): system wants to transmit IPv4 pkt to 176.16.222.1 (53 bytes)

These are all inside the netns used by "modem":

# ip addr
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
3: modem4: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 500
    link/none
    inet 176.16.222.3/30 scope global modem4
       valid_lft forever preferred_lft forever
    inet6 fe80::75d:7419:9433:6fee/64 scope link stable-privacy proto kernel_ll
       valid_lft forever preferred_lft forever

# ip l
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
3: modem4: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN mode DEFAULT group default qlen 500
    link/none

"Activate PDP Context Accept" sent to the MS contains:

Maximum SDU size: 1520 octets (153)


Related issues

Related to OsmocomBB - Feature #5503: expose GPRS user plane via tun deviceFeedbackpespin03/29/2022

Actions
Related to OsmoGGSN (former OpenGGSN) - Feature #6298: osmo-ggsn not providing MTU of the GTP tunnel to the MSNew12/08/2023

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