From 98ec18f098e5ef68e3a8cc6954fcaf5a7fb8b7be Mon Sep 17 00:00:00 2001 From: pali <7141871+pali@users.noreply.github.com> Date: Mon, 15 Feb 2021 07:54:01 +0100 Subject: [PATCH] pppd: Fix compilation with older glibc or kernel headers (#248) MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit glibc versions prior to 2.24 do not define SOL_NETLINK and linux kernel versions prior to 4.3 do not define NETLINK_CAP_ACK. So add fallback definitions for these macros into pppd/sys-linux.c file. Also extend description why we call SOL_NETLINK/NETLINK_CAP_ACK option. Signed-off-by: Pali Rohár --- pppd/sys-linux.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/pppd/sys-linux.c b/pppd/sys-linux.c index 85033d9..50c4f2d 100644 --- a/pppd/sys-linux.c +++ b/pppd/sys-linux.c @@ -125,6 +125,14 @@ #include #include #include +/* glibc versions prior to 2.24 do not define SOL_NETLINK */ +#ifndef SOL_NETLINK +#define SOL_NETLINK 270 +#endif +/* linux kernel versions prior to 4.3 do not define/support NETLINK_CAP_ACK */ +#ifndef NETLINK_CAP_ACK +#define NETLINK_CAP_ACK 10 +#endif #endif #include "pppd.h" @@ -2843,7 +2851,15 @@ static int append_peer_ipv6_address(unsigned int iface, struct in6_addr *local_a if (fd < 0) return 0; - /* do not ask for error message content */ + /* + * Tell kernel to not send to us payload of acknowledgment error message. + * NETLINK_CAP_ACK option is supported since Linux kernel version 4.3 and + * older kernel versions always send full payload in acknowledgment netlink + * message. We ignore payload of this message as we need only error code, + * to check if our set remote peer address request succeeded or failed. + * So ignore return value from the following setsockopt() call as setting + * option NETLINK_CAP_ACK means for us just a kernel hint / optimization. + */ one = 1; setsockopt(fd, SOL_NETLINK, NETLINK_CAP_ACK, &one, sizeof(one)); -- 2.39.2