libslirp, darwin.linux-builder: fix DNS resolution using libslirp on MacOS (#398952)

      };

    };

    # DNS fails for QEMU user networking (SLiRP) on macOS.  See:

    #

    # https://github.com/utmapp/UTM/issues/2353

    #

    # This works around that by using a public DNS server other than the DNS

    # server that QEMU provides (normally 10.0.2.3)

    networking.nameservers = [ "8.8.8.8" ];

    # The linux builder is a lightweight VM for remote building; not evaluation.

    nix.channel.enable = false;

From 735904142f95d0500c0eae6bf763e4ad24b6b9fd Mon Sep 17 00:00:00 2001

From: Samuel Thibault <samuel.thibault@ens-lyon.org>

Date: Wed, 26 Mar 2025 08:42:35 +0100

Subject: [PATCH] apple: Fix getting IPv4 DNS server address when IPv4 and IPv4

 are interleaved

When getting an IPv4 DNS server address, if libresolv returns

IPv4

IPv6

IPv4

IPv6

(or just IPv4 and IPv6)

we would still have found == 1 on the second iteration and thus take the

IPv6 even if it's not the proper af. We can as well just completely ignore

the non-matching af entries.

Fixes #85

---

 src/slirp.c | 7 +++++--

 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/slirp.c b/src/slirp.c

index bccee53..62a018a 100644

--- a/src/slirp.c

+++ b/src/slirp.c

@@ -289,9 +289,12 @@ static int get_dns_addr_libresolv(int af, void *pdns_addr, void *cached_addr,

     found = 0;

     DEBUG_MISC("IP address of your DNS(s):");

     for (int i = 0; i < count; i++) {

-        if (af == servers[i].sin.sin_family) {

-            found++;

+        if (af != servers[i].sin.sin_family) {

+            continue;

         }

+

+        found++;

+

         if (af == AF_INET) {

             addr = &servers[i].sin.sin_addr;

         } else { // af == AF_INET6

-- 

GitLab

    sha256 = "sha256-Eqdw6epFkLv4Dnw/s1pcKW0P70ApZwx/J2VkCwn50Ew=";

  };

  patches = [

    # https://gitlab.freedesktop.org/slirp/libslirp/-/commit/735904142f95d0500c0eae6bf763e4ad24b6b9fd

    # Vendorized due to frequent instability of the upstream repository.

    ./fix-dns-for-darwin.patch

  ];

  separateDebugInfo = true;

  nativeBuildInputs = [