Fix build with skalibs 2.10.0.0; document dependencies

1 files changed, 42 insertions, 28 deletions

diff --git a/INSTALL b/INSTALL
index 37e0076..b7f9a64 100644
--- a/INSTALL
+++ b/INSTALL
@@ -6,13 +6,15 @@ Build Instructions
 
   - A POSIX-compliant C development environment
   - GNU make version 3.81 or later
-  - skalibs version 2.9.4.0 or later: https://skarnet.org/software/skalibs/
-  - (Optional) execline version 2.6.1.1 or later: https://skarnet.org/software/execline/
-  - s6 version 2.9.2.0 or later: https://skarnet.org/software/s6/
+  - skalibs version 2.10.0.0 or later: https://skarnet.org/software/skalibs/
+  - (Optional) execline version 2.7.0.0 or later: https://skarnet.org/software/execline/
+  - s6 version 2.10.0.0 or later: https://skarnet.org/software/s6/
   - s6-dns version 2.3.3.0 or later: https://skarnet.org/software/s6-dns/
   - Depending on whether you build the SSL tools,
-        libressl version 3.1.4 or later: https://libressl.org/
-     or bearssl version 0.6 or later: https://bearssl.org/
+        bearssl version 0.6 or later: https://bearssl.org/
+     or libressl version 3.2.2 or later: https://libressl.org/
+     or openssl version 1.1.1h or later: https://openssl.org/ *in addition to*
+        libretls version 3.3.0 or later: https://git.causal.agency/libretls/about/
 
  This software will run on any operating system that implements
 POSIX.1-2008, available at:
@@ -182,14 +184,22 @@ source tree if parallel builds are needed.
 * SSL support
   -----------
 
- s6-networking implements UCSPI tools for SSL/TLS connections: s6-tlsclient,
-s6-tlsserver, s6-tlsc and s6-tlsd. Those are built if you give the
---enable-ssl=<implementation> flag to configure. There are two supported
-values for <implementation>: libressl (in which case the tools will be
-built against libtls) and bearssl (in which case the tools will be built
-against libbearssl). You should install the relevant header and library
-files for your chosen implementation, be it LibreSSL or BearSSL, before
-building a SSL-enabled s6-networking.
+ s6-networking implements UCSPI tools for SSL/TLS connections: see the
+doc/tls-overview.html page for a listing of these tools and what they do.
+The TLS tools are built if you give the --enable-ssl=<implementation>
+flag to configure. There are two supported values for <implementation>:
+bearssl and libtls. You should install the relevant header and library
+files for your chosen implementation before building a SSL-enabled
+s6-networking.
+ "bearssl" uses the BearSSL API, of which there's only one implementation,
+from bearssl.org.
+ "libtls" uses the libtls API, which has two possible implementations:
+ - The original one, from libressl.org, bundled with LibreSSL
+ - An alternative one, from causal.agency, that is used on top of
+OpenSSL.
+
+ For compatibility, "libressl" is accepted as <implementation> and is
+an alias to libtls.
 
  If your SSL headers and library files are not installed in /usr/include
 and /usr/lib, you can use the --with-ssl-path=DIR configure option:
@@ -198,23 +208,27 @@ DIR/lib. For more complex setups, use the generic --with-include and
 --with-dir configure options.
 
  If you choose --enable-ssl=bearssl, then s6-networking will build a
-"libsbearssl" support library, which s6-tlsc and s6-tlsd will be linked
-against. This support library depends on libbearssl interfaces.
-
- If you choose --enable-ssl=libressl, then s6-networking will build
-a "libstls" support library, which s6-tlsc and s6-tlsd will be linked
-against. This support library depends on libtls interfaces, but not
-on libssl or libcrypto interfaces - so it is possible to use alternative
-implementations of the libtls API.
+"libsbearssl" support library, which s6-tlsc-io and s6-tlsd-io will be
+linked against. This support library depends on libbearssl interfaces.
+
+ If you choose --enable-ssl=libtls, then s6-networking will build a
+"libstls" support library, which s6-tlsc-io and s6-tlsd-io will be
+linked against. This support library depends on libtls interfaces, but
+not on libssl or libcrypto interfaces, so it is possible to use other
+alternative implementations of the libtls API. There is one such
+implementation: libtls-bearssl, implementing libtls on top of bearssl,
+but using it with s6-networking is a waste since s6-networking supports
+bearssl natively.
 
  If your SSL implementation library needs nonstandard -l options to link
 against it, you can override the CRYPTO_LIB make variable.
-By default, CRYPTO_LIB is "-lbearssl" when building against BearSSL,
-and "-ltls -lssl -lcrypto" when building against LibreSSL.
+By default, CRYPTO_LIB is "-lbearssl" when building against bearssl,
+and "-ltls -lssl -lcrypto" when building against libtls.
 
- As of 2019-02-12, please note that BearSSL is considered beta quality
+ As of 2020-11-30, please note that BearSSL is considered beta quality
 by its author, so use with caution. Nevertheless, it's an incredibly
-promising library with high-quality interfaces and implementation.
-When statically linked against BearSSL, the s6-tlsc and s6-tlsd binaries
-are 1/10th the size of what they are when statically linked against LibreSSL,
-with a smaller RAM footprint too.
+good beta, with high-quality interfaces and implementation, and no
+known serious bugs.
+When statically linked against BearSSL, the s6-tlsc-io and s6-tlsd-io
+binaries are 1/10th the size of what they are when statically linked
+against libressl/openssl, with a much smaller RAM footprint too.