server: allow acceptor to send alerts after error

[djc]

Fixes #1792.

• Acceptor's accept and into_connection fns now return both an Error and an AcceptedAlert in the error case. The AcceptedAlert can be used to write any TLS alerts produced during processing.
• Test coverage is updated to include:
  • Tests for a junk handshake being rejected in accept with an alert produced
  • Tests for an incompatible handshake being rejected in into_connection with an alert produced
• The existing server_acceptor.rs example program is updated to demonstrate using the AcceptedAlert return to write alerts.

[rustls-benchmarking]

Benchmark results

Instruction counts

Significant differences

There are no significant instruction count differences

Other differences

Click to expand

Scenario	Baseline	Candidate	Diff	Threshold
handshake_session_id_aws_lc_rs_1.2_rsa_aes_server	4054867	4004375	-50492 (-1.25%)	3.58%
handshake_tickets_aws_lc_rs_1.2_rsa_aes_server	4510232	4471437	-38795 (-0.86%)	2.64%
handshake_session_id_aws_lc_rs_1.2_rsa_aes_client	4181784	4198571	16787 (0.40%)	0.95%
handshake_no_resume_aws_lc_rs_1.2_rsa_aes_server	12283118	12330378	47260 (0.38%)	1.27%
handshake_no_resume_aws_lc_rs_1.3_rsa_aes_server	12647197	12680789	33592 (0.27%)	0.88%
handshake_no_resume_aws_lc_rs_1.3_rsa_chacha_server	12726369	12693090	-33279 (-0.26%)	0.93%
handshake_session_id_aws_lc_rs_1.3_ecdsap384_chacha_client	30193496	30251925	58429 (0.19%)	0.45%
handshake_tickets_aws_lc_rs_1.3_rsa_chacha_server	32575291	32625728	50437 (0.15%)	0.83%
handshake_no_resume_aws_lc_rs_1.3_ecdsap384_aes_client	8650004	8638394	-11610 (-0.13%)	0.96%
handshake_tickets_ring_1.2_rsa_aes_client	4711654	4717388	5734 (0.12%)	0.74%
handshake_session_id_aws_lc_rs_1.3_rsa_chacha_server	32411841	32373031	-38810 (-0.12%)	0.43%
handshake_no_resume_ring_1.3_ecdsap256_chacha_server	2129022	2126536	-2486 (-0.12%)	0.31%
handshake_no_resume_aws_lc_rs_1.3_ecdsap384_chacha_client	8684087	8674043	-10044 (-0.12%)	0.78%
handshake_no_resume_ring_1.3_ecdsap256_aes_client	3897614	3893437	-4177 (-0.11%)	0.20%
handshake_tickets_aws_lc_rs_1.3_ecdsap256_chacha_server	32626382	32596279	-30103 (-0.09%)	0.29%
handshake_tickets_aws_lc_rs_1.3_rsa_aes_server	32664318	32636029	-28289 (-0.09%)	0.61%
handshake_session_id_ring_1.3_ecdsap256_aes_server	43554727	43519001	-35726 (-0.08%)	0.20%
handshake_tickets_ring_1.2_rsa_aes_server	4762153	4765988	3835 (0.08%)	0.60%
handshake_session_id_aws_lc_rs_1.3_rsa_aes_server	32461236	32436732	-24504 (-0.08%)	0.52%
handshake_session_id_aws_lc_rs_1.3_ecdsap384_aes_client	30235713	30258273	22560 (0.07%)	0.49%
handshake_session_id_ring_1.3_rsa_aes_server	43534510	43563371	28861 (0.07%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_rsa_aes_server	46270556	46240997	-29559 (-0.06%)	0.32%
handshake_tickets_ring_1.3_rsa_aes_server	43790799	43763663	-27136 (-0.06%)	0.20%
transfer_no_resume_aws_lc_rs_1.2_rsa_aes_server	46218453	46190842	-27611 (-0.06%)	0.32%
handshake_no_resume_aws_lc_rs_1.3_ecdsap256_chacha_client	3344101	3342120	-1981 (-0.06%)	0.23%
handshake_no_resume_ring_1.3_ecdsap256_chacha_client	3899206	3896900	-2306 (-0.06%)	0.35%
handshake_session_id_ring_1.2_rsa_aes_server	4327720	4330038	2318 (0.05%)	0.52%
handshake_session_id_aws_lc_rs_1.3_rsa_aes_client	30444619	30430060	-14559 (-0.05%)	0.21%
handshake_tickets_aws_lc_rs_1.3_ecdsap384_aes_client	30438332	30424288	-14044 (-0.05%)	0.51%
handshake_tickets_aws_lc_rs_1.3_ecdsap256_aes_server	32596081	32610239	14158 (0.04%)	0.25%
handshake_tickets_ring_1.3_rsa_chacha_server	43734052	43715716	-18336 (-0.04%)	0.20%
handshake_tickets_aws_lc_rs_1.3_ecdsap256_chacha_client	30386318	30396879	10561 (0.03%)	0.30%
handshake_session_id_aws_lc_rs_1.3_ecdsap384_chacha_server	32399177	32410294	11117 (0.03%)	0.30%
handshake_tickets_aws_lc_rs_1.3_ecdsap384_chacha_client	30399991	30410065	10074 (0.03%)	0.27%
handshake_tickets_aws_lc_rs_1.3_ecdsap256_aes_client	30418114	30408453	-9661 (-0.03%)	0.31%
handshake_session_id_ring_1.3_ecdsap384_aes_client	41994151	42006811	12660 (0.03%)	0.20%
handshake_tickets_ring_1.3_rsa_aes_client	42396955	42384643	-12312 (-0.03%)	0.20%
handshake_session_id_ring_1.3_rsa_chacha_server	43442726	43430155	-12571 (-0.03%)	0.20%
handshake_tickets_aws_lc_rs_1.3_ecdsap384_aes_server	32602692	32611972	9280 (0.03%)	0.27%
transfer_no_resume_aws_lc_rs_1.3_rsa_chacha_server	80408261	80431071	22810 (0.03%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_ecdsap384_aes_client	57974950	57990997	16047 (0.03%)	0.22%
handshake_tickets_aws_lc_rs_1.3_rsa_aes_client	30642453	30634357	-8096 (-0.03%)	0.31%
handshake_tickets_aws_lc_rs_1.3_rsa_chacha_client	30628683	30621258	-7425 (-0.02%)	0.22%
handshake_session_id_ring_1.3_rsa_chacha_client	42123699	42133596	9897 (0.02%)	0.20%
handshake_tickets_ring_1.3_ecdsap384_chacha_server	43645722	43655819	10097 (0.02%)	0.21%
handshake_no_resume_aws_lc_rs_1.3_ecdsap256_aes_server	1878150	1878579	429 (0.02%)	0.21%
transfer_no_resume_aws_lc_rs_1.3_ecdsap384_chacha_server	80455194	80436874	-18320 (-0.02%)	0.20%
handshake_tickets_ring_1.3_rsa_chacha_client	42327846	42318355	-9491 (-0.02%)	0.20%
handshake_tickets_ring_1.3_ecdsap256_aes_client	42165340	42174361	9021 (0.02%)	0.20%
handshake_tickets_ring_1.3_ecdsap256_aes_server	43759668	43750881	-8787 (-0.02%)	0.33%
handshake_session_id_ring_1.3_rsa_aes_client	42208903	42200431	-8472 (-0.02%)	0.20%
handshake_session_id_aws_lc_rs_1.3_rsa_chacha_client	30426637	30421272	-5365 (-0.02%)	0.22%
handshake_session_id_aws_lc_rs_1.3_ecdsap256_chacha_client	30221356	30216186	-5170 (-0.02%)	0.22%
handshake_no_resume_aws_lc_rs_1.3_ecdsap384_aes_server	4256873	4256192	-681 (-0.02%)	0.20%
handshake_tickets_ring_1.3_ecdsap384_aes_server	43741426	43747497	6071 (0.01%)	0.23%
handshake_session_id_ring_1.3_ecdsap256_aes_client	41994883	42000385	5502 (0.01%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_ecdsap384_chacha_client	92411965	92423840	11875 (0.01%)	0.20%
transfer_no_resume_ring_1.3_rsa_chacha_server	80343614	80353635	10021 (0.01%)	0.20%
handshake_session_id_ring_1.3_ecdsap384_aes_server	43546255	43551526	5271 (0.01%)	0.20%
handshake_session_id_ring_1.3_ecdsap384_chacha_server	43432030	43437283	5253 (0.01%)	0.20%
handshake_tickets_ring_1.3_ecdsap256_chacha_server	43680787	43686030	5243 (0.01%)	0.20%
handshake_session_id_ring_1.3_ecdsap384_chacha_client	41923089	41927998	4909 (0.01%)	0.20%
handshake_no_resume_ring_1.2_rsa_aes_server	12041884	12043229	1345 (0.01%)	0.20%
handshake_no_resume_ring_1.3_ecdsap256_aes_server	2126588	2126808	220 (0.01%)	0.31%
handshake_tickets_ring_1.3_ecdsap384_chacha_client	42099372	42103678	4306 (0.01%)	0.20%
handshake_session_id_ring_1.3_ecdsap256_chacha_client	41906453	41910553	4100 (0.01%)	0.20%
handshake_no_resume_ring_1.3_ecdsap384_chacha_server	13738065	13737079	-986 (-0.01%)	0.20%
handshake_tickets_aws_lc_rs_1.2_rsa_aes_client	4503508	4503192	-316 (-0.01%)	1.02%
transfer_no_resume_ring_1.3_ecdsap384_chacha_server	80350177	80355747	5570 (0.01%)	0.20%
handshake_no_resume_aws_lc_rs_1.3_ecdsap256_chacha_server	1881902	1882030	128 (0.01%)	0.20%
handshake_session_id_aws_lc_rs_1.3_ecdsap256_aes_client	30262488	30264338	1850 (0.01%)	0.34%
transfer_no_resume_ring_1.3_ecdsap256_chacha_server	80343899	80348472	4573 (0.01%)	0.20%
handshake_no_resume_ring_1.3_rsa_chacha_client	4547188	4547441	253 (0.01%)	0.20%
handshake_tickets_aws_lc_rs_1.3_ecdsap384_chacha_server	32589311	32587590	-1721 (-0.01%)	0.34%
transfer_no_resume_ring_1.3_ecdsap384_chacha_client	92392594	92397194	4600 (0.00%)	0.20%
handshake_no_resume_aws_lc_rs_1.2_rsa_aes_client	3151686	3151533	-153 (-0.00%)	0.20%
handshake_no_resume_aws_lc_rs_1.3_rsa_chacha_client	3365555	3365398	-157 (-0.00%)	0.20%
handshake_session_id_ring_1.2_rsa_aes_client	4443383	4443182	-201 (-0.00%)	0.85%
transfer_no_resume_ring_1.3_ecdsap256_chacha_client	92395516	92399689	4173 (0.00%)	0.20%
handshake_session_id_ring_1.3_ecdsap256_chacha_server	43438220	43440106	1886 (0.00%)	0.20%
handshake_no_resume_ring_1.3_rsa_chacha_server	12246317	12246837	520 (0.00%)	0.20%
handshake_session_id_aws_lc_rs_1.3_ecdsap256_aes_server	32417956	32416600	-1356 (-0.00%)	0.20%
handshake_tickets_ring_1.3_ecdsap384_aes_client	42167266	42169004	1738 (0.00%)	0.20%
handshake_tickets_ring_1.3_ecdsap256_chacha_client	42105888	42104325	-1563 (-0.00%)	0.20%
handshake_no_resume_ring_1.3_ecdsap384_aes_server	13734555	13734066	-489 (-0.00%)	0.20%
transfer_no_resume_ring_1.3_ecdsap256_aes_client	58064479	58066513	2034 (0.00%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_ecdsap256_aes_client	57964042	57965913	1871 (0.00%)	0.20%
handshake_no_resume_ring_1.2_rsa_aes_client	4440164	4440307	143 (0.00%)	0.20%
handshake_session_id_aws_lc_rs_1.3_ecdsap256_chacha_server	32410375	32409394	-981 (-0.00%)	0.30%
transfer_no_resume_aws_lc_rs_1.3_ecdsap256_aes_server	46265826	46264524	-1302 (-0.00%)	0.25%
transfer_no_resume_aws_lc_rs_1.3_ecdsap384_aes_server	46254553	46255769	1216 (0.00%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_ecdsap256_chacha_client	92434105	92436401	2296 (0.00%)	0.20%
transfer_no_resume_ring_1.3_ecdsap384_aes_server	46297539	46298688	1149 (0.00%)	0.20%
handshake_no_resume_aws_lc_rs_1.3_rsa_aes_client	3354664	3354743	79 (0.00%)	0.20%
transfer_no_resume_ring_1.2_rsa_aes_server	46176877	46175865	-1012 (-0.00%)	0.20%
transfer_no_resume_ring_1.3_ecdsap384_aes_client	58058954	58060032	1078 (0.00%)	0.20%
handshake_no_resume_ring_1.3_ecdsap384_aes_client	35453041	35452428	-613 (-0.00%)	0.20%
handshake_session_id_aws_lc_rs_1.3_ecdsap384_aes_server	32433402	32433928	526 (0.00%)	0.25%
transfer_no_resume_ring_1.3_rsa_chacha_client	92397280	92398664	1384 (0.00%)	0.20%
handshake_no_resume_aws_lc_rs_1.3_ecdsap384_chacha_server	4260939	4260986	47 (0.00%)	0.20%
handshake_no_resume_ring_1.3_ecdsap384_chacha_client	35455078	35454712	-366 (-0.00%)	0.20%
handshake_no_resume_ring_1.3_rsa_aes_server	12237054	12237151	97 (0.00%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_rsa_aes_client	57986093	57986437	344 (0.00%)	0.20%
transfer_no_resume_ring_1.3_ecdsap256_aes_server	46293203	46293463	260 (0.00%)	0.25%
transfer_no_resume_ring_1.2_rsa_aes_client	57920793	57920526	-267 (-0.00%)	0.20%
transfer_no_resume_aws_lc_rs_1.2_rsa_aes_client	68385903	68386194	291 (0.00%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_rsa_chacha_client	92454874	92454648	-226 (-0.00%)	0.20%
transfer_no_resume_ring_1.3_rsa_aes_server	46290592	46290666	74 (0.00%)	0.20%
handshake_no_resume_aws_lc_rs_1.3_ecdsap256_aes_client	3340182	3340186	4 (0.00%)	0.20%
handshake_no_resume_ring_1.3_rsa_aes_client	4537916	4537920	4 (0.00%)	0.20%
transfer_no_resume_ring_1.3_rsa_aes_client	58064348	58064324	-24 (-0.00%)	0.20%
transfer_no_resume_aws_lc_rs_1.3_ecdsap256_chacha_server	80454970	80454996	26 (0.00%)	0.20%

Wall-time

Significant differences

There are no significant wall-time differences

Other differences

Click to expand

Scenario	Baseline	Candidate	Diff	Threshold
transfer_no_resume_aws_lc_rs_1.3_ecdsap256_aes	4.75 ms	4.83 ms	0.09 ms (1.81%)	4.39%
transfer_no_resume_aws_lc_rs_1.3_ecdsap384_aes	5.46 ms	5.55 ms	0.09 ms (1.63%)	3.75%
transfer_no_resume_aws_lc_rs_1.3_rsa_aes	5.69 ms	5.78 ms	0.09 ms (1.57%)	2.81%
transfer_no_resume_ring_1.3_ecdsap256_aes	6.57 ms	6.67 ms	0.10 ms (1.53%)	3.46%
transfer_no_resume_ring_1.3_rsa_aes	7.15 ms	7.25 ms	0.10 ms (1.41%)	2.53%
handshake_no_resume_aws_lc_rs_1.3_ecdsap256_aes	474.67 µs	480.87 µs	6.20 µs (1.31%)	2.23%
transfer_no_resume_ring_1.2_rsa_aes	7.05 ms	7.14 ms	0.09 ms (1.27%)	2.97%
transfer_no_resume_aws_lc_rs_1.2_rsa_aes	5.69 ms	5.76 ms	0.07 ms (1.23%)	3.45%
handshake_no_resume_ring_1.3_ecdsap256_aes	504.18 µs	510.10 µs	5.92 µs (1.18%)	2.41%
handshake_no_resume_aws_lc_rs_1.3_ecdsap256_chacha	474.33 µs	479.72 µs	5.39 µs (1.14%)	2.90%
handshake_no_resume_ring_1.3_ecdsap256_chacha	502.70 µs	508.03 µs	5.33 µs (1.06%)	2.28%
transfer_no_resume_ring_1.3_ecdsap384_aes	9.67 ms	9.77 ms	0.10 ms (1.01%)	2.50%
handshake_session_id_aws_lc_rs_1.3_ecdsap256_chacha	5.42 ms	5.47 ms	0.05 ms (0.91%)	2.09%
handshake_tickets_aws_lc_rs_1.3_ecdsap256_chacha	5.46 ms	5.50 ms	0.05 ms (0.90%)	2.54%
handshake_tickets_aws_lc_rs_1.3_ecdsap384_chacha	6.16 ms	6.21 ms	0.05 ms (0.89%)	2.11%
handshake_no_resume_ring_1.3_rsa_chacha	1.08 ms	1.09 ms	0.01 ms (0.87%)	1.00%
handshake_session_id_aws_lc_rs_1.3_rsa_chacha	6.41 ms	6.46 ms	0.05 ms (0.79%)	2.09%
handshake_session_id_aws_lc_rs_1.3_ecdsap384_chacha	6.11 ms	6.16 ms	0.05 ms (0.76%)	1.86%
transfer_no_resume_aws_lc_rs_1.3_ecdsap256_chacha	13.23 ms	13.33 ms	0.10 ms (0.73%)	1.48%
handshake_session_id_ring_1.3_rsa_chacha	7.47 ms	7.53 ms	0.05 ms (0.69%)	2.26%
handshake_session_id_ring_1.3_rsa_aes	7.52 ms	7.58 ms	0.05 ms (0.69%)	1.78%
transfer_no_resume_aws_lc_rs_1.3_rsa_chacha	14.18 ms	14.27 ms	0.10 ms (0.68%)	1.41%
transfer_no_resume_ring_1.3_rsa_chacha	13.81 ms	13.91 ms	0.09 ms (0.68%)	1.55%
transfer_no_resume_ring_1.3_ecdsap256_chacha	13.24 ms	13.33 ms	0.09 ms (0.68%)	1.63%
handshake_tickets_ring_1.2_rsa_aes	1.85 ms	1.86 ms	0.01 ms (0.67%)	1.63%
handshake_tickets_aws_lc_rs_1.3_rsa_chacha	6.45 ms	6.49 ms	0.04 ms (0.67%)	2.19%
handshake_session_id_aws_lc_rs_1.3_ecdsap256_aes	5.44 ms	5.47 ms	0.04 ms (0.67%)	1.92%
transfer_no_resume_aws_lc_rs_1.3_ecdsap384_chacha	13.94 ms	14.03 ms	0.09 ms (0.65%)	1.64%
handshake_session_id_aws_lc_rs_1.3_rsa_aes	6.44 ms	6.47 ms	0.04 ms (0.61%)	1.72%
handshake_session_id_aws_lc_rs_1.3_ecdsap384_aes	6.15 ms	6.18 ms	0.04 ms (0.61%)	1.72%
handshake_no_resume_ring_1.3_rsa_aes	1.08 ms	1.09 ms	0.01 ms (0.60%)	1.00%
transfer_no_resume_ring_1.3_ecdsap384_chacha	16.34 ms	16.43 ms	0.09 ms (0.57%)	1.50%
handshake_session_id_ring_1.3_ecdsap256_aes	6.89 ms	6.93 ms	0.04 ms (0.57%)	1.81%
handshake_session_id_ring_1.3_ecdsap256_chacha	6.85 ms	6.89 ms	0.04 ms (0.57%)	2.28%
handshake_tickets_aws_lc_rs_1.3_ecdsap256_aes	5.47 ms	5.50 ms	0.03 ms (0.57%)	2.26%
handshake_tickets_ring_1.3_ecdsap256_aes	6.92 ms	6.96 ms	0.04 ms (0.55%)	1.90%
handshake_tickets_ring_1.3_ecdsap256_chacha	6.86 ms	6.90 ms	0.04 ms (0.55%)	2.05%
handshake_tickets_aws_lc_rs_1.3_ecdsap384_aes	6.18 ms	6.21 ms	0.03 ms (0.48%)	1.87%
handshake_session_id_ring_1.3_ecdsap384_chacha	9.95 ms	9.99 ms	0.05 ms (0.47%)	1.94%
handshake_no_resume_aws_lc_rs_1.3_ecdsap384_aes	1.19 ms	1.19 ms	0.01 ms (0.47%)	1.00%
handshake_tickets_ring_1.3_rsa_aes	7.56 ms	7.59 ms	0.03 ms (0.46%)	1.75%
handshake_tickets_ring_1.3_rsa_chacha	7.50 ms	7.53 ms	0.03 ms (0.44%)	2.03%
handshake_no_resume_aws_lc_rs_1.3_ecdsap384_chacha	1.18 ms	1.18 ms	0.00 ms (0.42%)	1.10%
handshake_no_resume_aws_lc_rs_1.3_rsa_chacha	1.41 ms	1.41 ms	0.01 ms (0.40%)	1.00%
handshake_tickets_aws_lc_rs_1.3_rsa_aes	6.46 ms	6.48 ms	0.02 ms (0.38%)	1.89%
handshake_session_id_ring_1.3_ecdsap384_aes	9.99 ms	10.03 ms	0.04 ms (0.37%)	1.69%
handshake_no_resume_ring_1.2_rsa_aes	1.07 ms	1.08 ms	0.00 ms (0.34%)	1.05%
handshake_tickets_ring_1.3_ecdsap384_chacha	9.97 ms	10.01 ms	0.03 ms (0.33%)	2.27%
handshake_tickets_ring_1.3_ecdsap384_aes	10.02 ms	10.05 ms	0.03 ms (0.31%)	2.20%
handshake_no_resume_aws_lc_rs_1.2_rsa_aes	1.36 ms	1.37 ms	0.00 ms (0.30%)	1.02%
handshake_tickets_aws_lc_rs_1.2_rsa_aes	2.34 ms	2.34 ms	0.01 ms (0.24%)	1.73%
handshake_no_resume_aws_lc_rs_1.3_rsa_aes	1.41 ms	1.42 ms	0.00 ms (0.22%)	1.00%
handshake_no_resume_ring_1.3_ecdsap384_chacha	3.61 ms	3.61 ms	0.01 ms (0.17%)	1.33%
handshake_session_id_ring_1.2_rsa_aes	1.76 ms	1.76 ms	0.00 ms (0.09%)	2.57%
handshake_no_resume_ring_1.3_ecdsap384_aes	3.61 ms	3.61 ms	0.00 ms (0.09%)	1.11%
handshake_session_id_aws_lc_rs_1.2_rsa_aes	2.18 ms	2.18 ms	0.00 ms (0.03%)	1.51%

Additional information

Historical results

Checkout details:

• Base repo: https://github.com/rustls/rustls.git
• Base branch: main (64f9742)
• Candidate repo: https://github.com/rustls/rustls.git
• Candidate branch: acceptor-alerts (6d7569e)

[codecov]

Codecov Report

Attention: Patch coverage is 82.92683% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 95.95%. Comparing base (64f9742) to head (6d7569e).

Files	Patch %	Lines
rustls/src/server/server_conn.rs	82.92%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1811      +/-   ##
==========================================
- Coverage   95.98%   95.95%   -0.04%     
==========================================
  Files          84       84              
  Lines       18791    18819      +28     
==========================================
+ Hits        18036    18057      +21     
- Misses        755      762       +7     

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[ctz]

Yes would be good to have at least two test cases for this: one where the clienthello is just junk (so accept() fails & and sends eg decode_error), another where the handshake is impossible (so into_connection() fails and sends eg handshake_failure)

They other thing we should do in this PR is make examples/src/bin/server_acceptor.rs send alerts; so it makes a good starting point for people to crib from.

[djc]

I probably won't be able contribute the test/example work this week.

[cpu]

I probably won't be able contribute the test/example work this week.

I'm looking at this now (but won't push to this branch myself since it seems like you're also rebasing ATM)

one where the clienthello is just junk (so accept() fails & and sends eg decode_error)

I think 2a60b63 would meet your requirement

another where the handshake is impossible (so into_connection() fails and sends eg handshake_failure)

Working on this one now.

They other thing we should do in this PR is make examples/src/bin/server_acceptor.rs send alerts; so it makes a good starting point for people to crib from.

Here's an example update commit: d01215a

I think we might want Debug on Accepted as well. I was surprised that writing let err_result = acceptor.accept().unwrap_err(); apparently requires it:

Here's that fix: 0c8c0c3

[djc]

Rebased this. Feel free to take the baton for this branch!

[cpu]

Feel free to take the baton for this branch!

🤝

I completed the requested test coverage and rolled it and the one new Debug impl into the original commit. I tacked on a second commit that updates the acceptor example to write alerts.

I've updated the PR description and I think this is now ready for review.

[djc]

LGTM, thanks for taking care of the tests/examples.