Delete becomes very, very fast - almost free, but after setsockopt() syscall returns, the key is still alive until next RCU grace period. Which is fine for listen sockets as userspace needs to be aware of setsockopt(TCP_AO) and accept() race and resolve it with verification by getsockopt() after TCP connection was accepted. The benchmark results (on non-loaded box, worse with more RCU work pending): > ok 33 Worst case delete 16384 keys: min=5ms max=10ms mean=6.93904ms stddev=0.263421 > ok 34 Add a new key 16384 keys: min=1ms max=4ms mean=2.17751ms stddev=0.147564 > ok 35 Remove random-search 16384 keys: min=5ms max=10ms mean=6.50243ms stddev=0.254999 > ok 36 Remove async 16384 keys: min=0ms max=0ms mean=0.0296107ms stddev=0.0172078
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| @@ -396,7 +396,8 @@ struct tcp_ao_del { /* setsockopt(TCP_AO_DEL_KEY) */ · 395 unmodified lines | ||
| 396 | 396 | __s32 ifindex; /* L3 dev index for VRF */ |
| 397 | 397 | __u32 set_current :1, /* corresponding ::current_key */ |
| 398 | 398 | set_rnext :1, /* corresponding ::rnext */ |
| 399 | − reserved :30; /* must be 0 */ | |
| 399 | + del_async :1, /* only valid for listen sockets */ | |
| 400 | + reserved :29; /* must be 0 */ | |
| 400 | 401 | __u16 reserved2; /* padding, must be 0 */ |
| 401 | 402 | __u8 prefix; /* peer's address prefix */ |
| 402 | 403 | __u8 sndid; /* SendID for outgoing segments */ |