From 35a3eb9bdc95d1e6ba25bc65c78959ea104e45a1 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 27 May 2020 19:27:51 +0200
Subject: [PATCH] socket-util: add generic socket_pass_pktinfo() helper

The helper turns on the protocol specific "packet info" structure cmsg
for three relevant protocols we know.
---
 src/basic/socket-util.c | 24 +++++++++++++++++++++++-
 src/basic/socket-util.h |  2 ++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
index 0be098df2e..05dd7e7001 100644
--- a/src/basic/socket-util.c
+++ b/src/basic/socket-util.c
@@ -1174,5 +1174,27 @@ ssize_t recvmsg_safe(int sockfd, struct msghdr *msg, int flags) {
         }
 
         return n;
-
+}
+
+int socket_pass_pktinfo(int fd, bool b) {
+        int af;
+        socklen_t sl = sizeof(af);
+
+        if (getsockopt(fd, SOL_SOCKET, SO_DOMAIN, &af, &sl) < 0)
+                return -errno;
+
+        switch (af) {
+
+        case AF_INET:
+                return setsockopt_int(fd, IPPROTO_IP, IP_PKTINFO, b);
+
+        case AF_INET6:
+                return setsockopt_int(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, b);
+
+        case AF_NETLINK:
+                return setsockopt_int(fd, SOL_NETLINK, NETLINK_PKTINFO, b);
+
+        default:
+                return -EAFNOSUPPORT;
+        }
 }
diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
index 6f366c0429..9e02e39887 100644
--- a/src/basic/socket-util.h
+++ b/src/basic/socket-util.h
@@ -220,3 +220,5 @@ int socket_bind_to_ifname(int fd, const char *ifname);
 int socket_bind_to_ifindex(int fd, int ifindex);
 
 ssize_t recvmsg_safe(int sockfd, struct msghdr *msg, int flags);
+
+int socket_pass_pktinfo(int fd, bool b);