From c2fbcde4449ffaf798f9ba4f742b942d33a1c1c8 Mon Sep 17 00:00:00 2001
From: Gregor Kleen <gkleen@yggdrasil.li>
Date: Fri, 10 Mar 2023 22:24:40 +0100
Subject: libdscp

---
 overlays/libdscp/default.nix   | 11 +++++++++++
 overlays/libdscp/src/Makefile  | 16 ++++++++++++++++
 overlays/libdscp/src/libdscp.c | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)
 create mode 100644 overlays/libdscp/default.nix
 create mode 100644 overlays/libdscp/src/Makefile
 create mode 100644 overlays/libdscp/src/libdscp.c

(limited to 'overlays')

diff --git a/overlays/libdscp/default.nix b/overlays/libdscp/default.nix
new file mode 100644
index 00000000..47103fd3
--- /dev/null
+++ b/overlays/libdscp/default.nix
@@ -0,0 +1,11 @@
+{ final, prev, ... }:
+{
+  libdscp = prev.stdenv.mkDerivation {
+    pname = "libdscp";
+    version = "0.0.0";
+
+    src = ./src;
+
+    makeFlags = [ "PREFIX=$(out)" ];
+  };
+}
diff --git a/overlays/libdscp/src/Makefile b/overlays/libdscp/src/Makefile
new file mode 100644
index 00000000..e76930d7
--- /dev/null
+++ b/overlays/libdscp/src/Makefile
@@ -0,0 +1,16 @@
+ifeq ($(PREFIX),)
+    PREFIX := /usr/local
+endif
+
+.PHONY: all install
+
+all: libdscp
+
+libdscp:
+	$(CC) \
+		-o $@.so $@.c \
+		-D_GNU_SOURCE \
+		-nostartfiles -shared
+install: libdscp
+	install -d $(DESTDIR)$(PREFIX)/lib/
+	install -m 644 libdscp.so $(DESTDIR)$(PREFIX)/lib/
diff --git a/overlays/libdscp/src/libdscp.c b/overlays/libdscp/src/libdscp.c
new file mode 100644
index 00000000..1bc9a16d
--- /dev/null
+++ b/overlays/libdscp/src/libdscp.c
@@ -0,0 +1,38 @@
+#include <dlfcn.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <arpa/inet.h>
+
+void _init(void);
+int (*sys_connect)(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
+int connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
+
+int dscp_val = 0;
+
+void _init(void) {
+  const char* err;
+
+  char* env_dscp;
+
+  env_dscp = getenv("DSCP");
+
+  if (env_dscp)
+    dscp_val = atoi(env_dscp) << 2;
+
+  sys_connect = dlsym(RTLD_NEXT, "connect");
+
+  err = dlerror();
+  if (err != NULL)
+    (void)fprintf(stderr, "libdscp:dlsym (connect): %s\n", err);
+}
+
+int connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen) {
+  int oerrno = errno;
+
+  setsockopt(sockfd, IPPROTO_IP, IP_TOS, &dscp_val, sizeof dscp_val);
+  setsockopt(sockfd, IPPROTO_IPV6, IPV6_TCLASS, &dscp_val, sizeof dscp_val);
+
+  errno = oerrno;
+  return sys_connect(sockfd, addr, addrlen);
+}
-- 
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