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Bug #6197
open"Cannot handle SM for unknown MM CTX"
Start date:
09/28/2023
Due date:
% Done:
0%
Spec Reference:
Description
I am observing relatively long PDP Context activation with Sony Ericsson K800i and recent osmo-sgsn:
osmo-sgsn 1.11.0
osmo-pcu 1.3.1.1-c1b0
I don't remember if this was the case before, most likely not.
As can be seen from the attached PCAP, the MS orders a PDP Context activation right after completing the Attach (frame 259):
130 16.160906108 127.0.0.1 → 127.0.0.1 GPRS-LLC 107 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 0(DTAP) (GMM) Attach Request 156 16.161190149 127.0.0.1 → 127.0.0.1 GPRS-LLC 86 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 0(DTAP) (GMM) Identity Request 157 16.797408334 127.0.0.1 → 127.0.0.1 GPRS-LLC 86 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 1(DTAP) (GMM) Identity Response 173 16.797533278 127.0.0.1 → 127.0.0.1 GPRS-LLC 86 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 1(DTAP) (GMM) Identity Request 181 17.200282825 127.0.0.1 → 127.0.0.1 GPRS-LLC 86 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 2(DTAP) (GMM) Identity Response 226 17.225222456 127.0.0.1 → 127.0.0.1 GPRS-LLC 113 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 2(DTAP) (GMM) Attach Accept 239 17.697504097 127.0.0.1 → 127.0.0.1 GPRS-LLC 77 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 3(DTAP) (GMM) Attach Complete 259 17.739056217 127.0.0.1 → 127.0.0.1 GPRS-LLC 136 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 4(DTAP) (SM) Activate PDP Context Request <-- (!) 274 17.739270297 127.0.0.1 → 127.0.0.1 GPRS-LLC 76 SAPI: LLGMM, U, XID 275 17.739280476 127.0.0.1 → 127.0.0.1 GPRS-LLC 75 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 0(DTAP) (GMM) Detach Request <-- (!)
The SGSN is responding with GMM Detach Request (frame 275), here is the related logging:
259 17.739056217 127.0.0.1 → 127.0.0.1 GPRS-LLC 136 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 4(DTAP) (SM) Activate PDP Context Request 260 17.739109847 127.0.0.1 → 127.0.5.1 GSMTAP 180 NSE(00101)-NSVC(00101) Rx NS-UNITDATA 261 17.739128332 127.0.0.1 → 127.0.5.1 GSMTAP 263 GPRS-NS2-VC(UDP-NSE00101-NSVC00101-0_0_0_0:23000-127_0_0_1:23023)[0x55e69ba253d0]{UNBLOCKED}: Received Event RX-UNITDATA 262 17.739139873 127.0.0.1 → 127.0.5.1 GSMTAP 180 NSE(00101)-NSVC(00101) Rx NS-UNITDATA 263 17.739148439 127.0.0.1 → 127.0.5.1 GSMTAP 183 BSSGP TLLI=0x85c79efb Rx UPLINK-UNITDATA 264 17.739181411 127.0.0.1 → 127.0.5.1 GSMTAP 236 LLME(ffffffff/85c79efb){UNASSIGNED} LLC RX: unknown TLLI 0x85c79efb, creating LLME on the fly 265 17.739188394 127.0.0.1 → 127.0.5.1 GSMTAP 193 LLC SAPI=1 C U GEA0 IOV-UI=0x000000 FCS=0x3ef88c 266 17.739193033 127.0.0.1 → 127.0.5.1 GSMTAP 149 CMD=UI 267 17.739196720 127.0.0.1 → 127.0.5.1 GSMTAP 147 DATA 268 17.739200627 127.0.0.1 → 127.0.5.1 GSMTAP 143 269 17.739212048 127.0.0.1 → 127.0.5.1 GSMTAP 214 LLME(ffffffff/85c79efb){UNASSIGNED} Cannot handle SM for unknown MM CTX 270 17.739224792 127.0.0.1 → 127.0.5.1 GSMTAP 198 LLME(ffffffff/85c79efb){UNASSIGNED} LLGM Reset (SAPI=1) 271 17.739243207 127.0.0.1 → 127.0.5.1 GSMTAP 180 NSE(00101)-NSVC(00101) Tx NS-UNITDATA 272 17.739252294 127.0.0.1 → 127.0.5.1 GSMTAP 215 <- GMM DETACH REQ (type: re-attach required, cause: Implicitly detached) 273 17.739257293 127.0.0.1 → 127.0.5.1 GSMTAP 180 NSE(00101)-NSVC(00101) Tx NS-UNITDATA 274 17.739270297 127.0.0.1 → 127.0.0.1 GPRS-LLC 76 SAPI: LLGMM, U, XID 275 17.739280476 127.0.0.1 → 127.0.0.1 GPRS-LLC 75 SAPI: LLGMM, UI, protected, non-ciphered information, N(U) = 0(DTAP) (GMM) Detach Request
The MS repeats the request again (frame 517) 30 seconds after the first attempt, and finally gets a PDP Context activated.
The key difference between frames 259 (first attempt) and 517 (second attempt) is TLLI indicated in the BSSGP header.
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