[PATCH 2/4] Makefile: Remove unused DUAL_STACK_SOCKETS define

[David Gibson <david@gibson.dropbear.id.au>]

We have a make variable DUAL_STACK_SOCKETS which used to determine whether
we'd use dual stack sockets.  When we introduced it we were concerned that
we might have future ports to systems which did not support them.

We've since discovered that the dual stack interface is described in
RFC 3493, and supported by both Windows and BSD.  Platforms sometimes
differ in the default setting for the IPV6_V6ONLY socket option, but the
feature itself is widely supported.  So, since b8d4fac6a2e7 ("util, pif:
Replace sock_l4() with pif_sock_l4()") we've simply assumed its presence.

The makefile still defines the now unused variable, though.  Remove it.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 Makefile | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/Makefile b/Makefile
index 0a0a60b0..a8c09815 100644
--- a/Makefile
+++ b/Makefile
@@ -11,10 +11,6 @@
 
 VERSION ?= $(shell git describe --tags HEAD 2>/dev/null || echo "unknown\ version")
 
-# Does the target platform allow IPv4 connections to be handled via
-# the IPv6 socket API? (Linux does)
-DUAL_STACK_SOCKETS := 1
-
 TARGET ?= $(shell $(CC) -dumpmachine)
 $(if $(TARGET),,$(error Failed to get target architecture))
 # Get 'uname -m'-like architecture description for target
@@ -33,7 +29,6 @@ endif
 BASE_CPPFLAGS := -D_XOPEN_SOURCE=700 -D_GNU_SOURCE $(FORTIFY_FLAG)
 BASE_CPPFLAGS += -DPAGE_SIZE=$(shell getconf PAGE_SIZE)
 BASE_CPPFLAGS += -DVERSION=\"$(VERSION)\"
-BASE_CPPFLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
 
 BASE_CFLAGS := -std=c11 -pie -fPIE -O2
 BASE_CFLAGS += -pedantic -Wall -Wextra -Wno-format-zero-length -Wformat-security
-- 
2.54.0