同问：

Server 侧日志：
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08[CFG] received stroke: add connection 'windows7'
08[CFG] adding virtual IP address pool 172.17.17.0/24
08[CFG] loaded certificate "C=CN, O=strongSwan, CN=x.x.x.x" from 'serverCert.pem'
08[CFG] id '%any' not confirmed by certificate, defaulting to 'C=CN, O=strongSwan, CN=x.x.x.x'
08[CFG] added configuration 'windows7'
10[NET] received packet: from 210.51.19.2[17553] to x.x.x.x[500] (388 bytes)
10[ENC] parsed IKE_SA_INIT request 0 [ SA KE No N(REDIR_SUP) N(NATD_S_IP) N(NATD_D_IP) N(FRAG_SUP) ]
10[IKE] 210.51.19.2 is initiating an IKE_SA
10[CFG] received proposals: IKE:AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024, IKE:AES_CBC_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/MODP_1536, IKE:3DES_CBC/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
10[CFG] configured proposals: IKE:AES_CBC_256/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
10[IKE] remote host is behind NAT
10[IKE] received proposals inacceptable
10[ENC] generating IKE_SA_INIT response 0 [ N(NO_PROP) ]
10[NET] sending packet: from x.x.x.x[500] to *.*.*.* [17553] (36 bytes)

Client 侧日志：
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Oct 12 11:02:36 Onion-iPhone-6S nesessionmanager[247] <Notice>: NESMIKEv2VPNSession[x.x.x.x:1FECCA55-2070-44C8-8214-E62DF31F6E0B]: status changed to connecting
Oct 12 11:02:36 Onion-iPhone-6S locationd[70] <Notice>: need a scan, count, 0, 0, lwatchdog, 0.0, interval, 60.0, needWatchdog, 0
Oct 12 11:02:36 Onion-iPhone-6S configd[38] <Notice>: network changed
Oct 12 11:02:36 Onion-iPhone-6S neagent[291] <Error>: Failed to process IKE SA Init packet
Oct 12 11:02:36 Onion-iPhone-6S neagent[291] <Notice>: BUG in libdispatch client: kevent[EVFILT_READ] delete: "Bad file descriptor" - 0x9

官方文档，不明觉厉
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https://wiki.strongswan.org/projects/strongswan/wiki/IOS_(Apple)#IKEv2-on-iOS-9-OS-X-1011-and-newer