The 2023 SIGCOMM paper "Improving Network Availability with Protective ReRoute" has indicated Linux TCP's RTO-triggered txhash rehashing can effectively reduce application disruption during outages. To better measure the efficacy of this feature, this patch adds three more detailed stats during RTO recovery and exports via TCP_INFO. Applications and monitoring systems can leverage this data to measure the network path diversity and end-to-end repair latency during network outages to improve their network infrastructure. The following counters are added to tcp_sock in order to track RTO events over the lifetime of a TCP socket. 1. u16 total_rto - Counts the total number of RTO timeouts. 2. u16 total_rto_recoveries - Counts the total number of RTO recoveries. 3. u32 total_rto_time - Counts the total time spent (ms) in RTO recoveries. (time spent in CA_Loss and CA_Recovery states) To compute total_rto_time, we add a new u32 rto_stamp field to tcp_sock. rto_stamp records the start timestamp (ms) of the last RTO recovery (CA_Loss). Corresponding fields are also added to the tcp_info struct.
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| @@ -289,6 +289,18 @@ struct tcp_info { · 288 unmodified lines | |||
| 289 | */ | 289 | */ |
| 290 | 290 | ||
| 291 | __u32 tcpi_rehash; /* PLB or timeout triggered rehash attempts */ | 291 | __u32 tcpi_rehash; /* PLB or timeout triggered rehash attempts */ |
| 292 | |||
| 293 | __u16 tcpi_total_rto; /* Total number of RTO timeouts, including | ||
| 294 | * SYN/SYN-ACK and recurring timeouts. | ||
| 295 | */ | ||
| 296 | __u16 tcpi_total_rto_recoveries; /* Total number of RTO | ||
| 297 | * recoveries, including any | ||
| 298 | * unfinished recovery. | ||
| 299 | */ | ||
| 300 | __u32 tcpi_total_rto_time; /* Total time spent in RTO recoveries | ||
| 301 | * in milliseconds, including any | ||
| 302 | * unfinished recovery. | ||
| 303 | */ | ||
| 292 | }; | 304 | }; |
| 293 | 305 | ||
| 294 | /* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */ | 306 | /* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */ |