• 配置选项 auto = ignore | add | route | start

英文文档:
https://wiki.strongswan.org/projects/strongswan/wiki/ConnSection

auto = ignore | add | route | start

what operation, if any, should be done automatically at IPsec startup.

auto=add loads a connection without starting it.
auto=route loads a connection and installs kernel traps. If traffic is detected between leftsubnet and rightsubnet, a connection is established.
auto=start loads a connection and brings it up immediately.
auto=ignore ignores the connection. This is equal to deleting a connection from the config file. Relevant only locally, other end need not agree on it.

译文1

配置选项 esp = <cipher suites>

comma-separated list of ESP encryption/authentication algorithms to be used for the connection, e.g:

esp=aes128-sha256

The notation is encryption-integrity[-dhgroup][-esnmode].

For IKEv2, multiple algorithms (separated by -) of the same type can be included in a single proposal.

IKEv1 only includes the first algorithm in a proposal. Only either the ah or the esp keyword may be used, AH+ESP bundles are not supported.

Defaults to aes128-sha256 (aes128-sha1, 3des-sha1 before 5.4.0). The daemon adds its extensive default proposal to this default or the configured value. To restrict it to the configured proposal an exclamation mark (!) can be added at the end.

Note:
As a responder, the daemon defaults to selecting the first configured proposal that's also supported by the peer. By disabling charon.prefer_configured_proposals in strongswan.conf this may be changed to selecting the first acceptable proposal sent by the peer instead.
In order to restrict a responder to only accept specific cipher suites, the strict flag (!, exclamation mark) can be used, e.g:

esp=aes256-sha512-modp4096!

If dh-group is specified, CHILD_SA rekeying and initial negotiation include a separate Diffe-Hellman exchange (since 5.0.0 this also applies to IKEv1 Quick Mode). However, for IKEv2, the keys of the CHILD_SA created implicitly with the IKE_SA will always be derived from the IKE_SA's key material. So any DH group specified here will only apply when the CHILD_SA is later rekeyed or is created with a separate CREATE_CHILD_SA exchange. Therefore, a proposal mismatch might not immediately be noticed when the SA is established, but may later cause rekeying to fail.

Valid values for esnmode are esn and noesn. Specifying both negotiates extended sequence number support with the peer, the default is noesn.

Refer to IKEv1CipherSuites and IKEv2CipherSuites for a list of valid keywords.

译文2: ESP 选项

encryption-integrity[-dhgroup][-esnmode]

对称加密算法-校验算法[-会话密钥交换算法][-有无ESN模式]
参见 https://wiki.strongswan.org/projects/strongswan/wiki/IKEv2CipherSuites

• esp=null-sha256 允许传输不加密的数据。
• esp=aes128-sha256 选择使用对称加密 AES128 搭配完整性校验 (HMAC)SHA256 算法，如果对端不支持则继续尝试其他组合。
• esp=aes256-sha512-modp4096!叹号表示强制使用某算法组，如果对端不接受则终止本次会话, 不再尝试其他算法组合。

配置选项 ike = <cipher suites>

comma-separated list of IKE/ISAKMP SA encryption/authentication algorithms to be used, e.g:

aes128-sha256-modp3072

The notation is encryption-integrity[-prf]-dhgroup. In IKEv2, multiple algorithms and proposals may be included, such as aes128-aes256-sha1-modp3072-modp2048,3des-sha1-md5-modp1024.

The ability to configure a PRF algorithm different to that defined for integrity protection was added with 5.0.2.

If no PRF is configured, the algorithms defined for integrity are proposed as PRF. The prf keywords are the same as the integrity algorithms, but have a prf prefix (such as prfsha1, prfsha256 or prfaesxcbc).

Defaults to:

aes128-sha256-modp3072

(aes128-sha1-modp2048,3des-sha1-modp1536 before 5.4.0) for IKEv1.

The daemon adds its extensive default proposal to this default or the configured value. To restrict it to the configured proposal an exclamation mark (!) can be added at the end.

Refer to IKEv1CipherSuites and IKEv2CipherSuites for a list of valid keywords.

Note: As a responder both daemons accept the first supported proposal received from the peer. In order
to restrict a responder to only accept specific cipher suites, the strict flag (!, exclamation mark)
can be used, e.g:

aes256-sha512-modp4096!

译文3: IKE选项

encryption-integrity[-prf]-dhgroup

对称加密算法-校验算法[-prf]-会话密钥交换算法
参见 https://wiki.strongswan.org/projects/strongswan/wiki/IKEv2CipherSuites

• 默认IKE协商算法为 aes128-sha256-modp3072 如果对端不支持则继续尝试其他组合。
• PRF: 默认套用哈希算法相一致的算法(例如sha1对应prfsha1)
• ! 叹号表示强制使用某算法组，如果对端不接受则终止本次会话, 不再尝试其他算法组合。

参考文档:

• https://wiki.strongswan.org/projects/strongswan/wiki/ConnSection
• https://github.com/strongswan/strongswan/blob/master/README_LEGACY.md