[tor-bugs] #23588 [Core Tor/Tor]: Write fascist_firewall_choose_address_ls() and use it in hs_get_extend_info_from_lspecs()

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#23588: Write fascist_firewall_choose_address_ls() and use it in
hs_get_extend_info_from_lspecs()
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  neel
     Type:  defect                               |         Status:
                                                 |  assigned
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  unspecified
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  prop224, tor-hs, single-onion,       |  Actual Points:
  ipv6, 034-triage-20180328,                     |
  034-removed-20180328                           |
Parent ID:  #23493                               |         Points:  1
 Reviewer:                                       |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by teor):

 Replying to [comment:8 neel]:
 > In `ed25519_cert.h`, `link_specifier_t`/`link_specifier_st` looks like
 this:
 >
 > {{{
 > struct link_specifier_st {
 >   uint8_t ls_type;
 >   uint8_t ls_len;
 >   uint32_t un_ipv4_addr;
 >   uint16_t un_ipv4_port;
 >   uint8_t un_ipv6_addr[16];
 >   uint16_t un_ipv6_port;
 >   uint8_t un_legacy_id[20];
 >   uint8_t un_ed25519_id[32];
 >   TRUNNEL_DYNARRAY_HEAD(, uint8_t) un_unrecognized;
 >   uint8_t trunnel_error_code_;
 > };
 > }}}
 >
 > But the `fascist_firewall_choose_address_*` family of functions defines
 DirPorts in the function, like this:
 >
 > {{{
 > static void
 > fascist_firewall_choose_address_base(const tor_addr_t *ipv4_addr,
 >                                      uint16_t ipv4_orport,
 >                                      uint16_t ipv4_dirport,
 >                                      const tor_addr_t *ipv6_addr,
 >                                      uint16_t ipv6_orport,
 >                                      uint16_t ipv6_dirport,
 >                                      firewall_connection_t
 fw_connection,
 >                                      int pref_only,
 >                                      int pref_ipv6,
 >                                      tor_addr_port_t* ap)
 > }}}
 >
 > Should I then assume the `ipv4_dirport` and `ipv6_dirport` is `0`?

 Yes, link specifiers are only defined for ORPorts.
 Also, #24732 will remove the IPv6 DirPort code, because it's unused.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/23588#comment:9>
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