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From 96681723232e9eb0182279086fef291283004806 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Wed, 27 May 2020 19:27:51 +0200
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Subject: [PATCH] socket-util: add generic socket_pass_pktinfo() helper
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The helper turns on the protocol specific "packet info" structure cmsg
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for three relevant protocols we know.
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(cherry picked from commit 35a3eb9bdc95d1e6ba25bc65c78959ea104e45a1)
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Related: #1887181
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---
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 src/basic/socket-util.c | 23 +++++++++++++++++++++++
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 src/basic/socket-util.h |  2 ++
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 2 files changed, 25 insertions(+)
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diff --git a/src/basic/socket-util.c b/src/basic/socket-util.c
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index 986bc6e67f..053bcba670 100644
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--- a/src/basic/socket-util.c
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+++ b/src/basic/socket-util.c
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@@ -1246,3 +1246,26 @@ int socket_ioctl_fd(void) {
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         return fd;
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 }
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+
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+int socket_pass_pktinfo(int fd, bool b) {
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+        int af;
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+        socklen_t sl = sizeof(af);
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+
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+        if (getsockopt(fd, SOL_SOCKET, SO_DOMAIN, &af, &sl) < 0)
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+                return -errno;
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+
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+        switch (af) {
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+
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+        case AF_INET:
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+                return setsockopt_int(fd, IPPROTO_IP, IP_PKTINFO, b);
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+
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+        case AF_INET6:
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+                return setsockopt_int(fd, IPPROTO_IPV6, IPV6_RECVPKTINFO, b);
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+
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+        case AF_NETLINK:
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+                return setsockopt_int(fd, SOL_NETLINK, NETLINK_PKTINFO, b);
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+
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+        default:
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+                return -EAFNOSUPPORT;
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+        }
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+}
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diff --git a/src/basic/socket-util.h b/src/basic/socket-util.h
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index 616f2e0d05..c7c9ad34d6 100644
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--- a/src/basic/socket-util.h
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+++ b/src/basic/socket-util.h
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@@ -190,3 +190,5 @@ static inline int setsockopt_int(int fd, int level, int optname, int value) {
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         return 0;
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 }
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+
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+int socket_pass_pktinfo(int fd, bool b);