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Date: Mon, 13 Jun 2022 11:41:57 -0400
From: Waldek Kozaczuk <>
Subject: netlink.c: missing handling of EAGAIN and EWOULDBLOCK


Very recently we implemented minimal rnetlink support on OSv side which
allowed us to finally switch to the netlink-based implementation of
getifaddrs() and if_nameindex().

However, I noticed that the function __netlink_enumerate() in uses
MSG_DONTWAIT flag when calling recv() which may fail with EAGAIN or
EWOULDBLOCK and there is no error/retry handling for that. I actually saw
both functions fail occasionally on OSv.

One way to fix is to add missing error handling. But another simpler
solution is to stop using MSG_DONTWAIT altogether and force recv() to
block. In other words, the line:

r = recv(fd, u.buf, sizeof(u.buf), MSG_DONTWAIT);

should change to:

r = recv(fd, u.buf, sizeof(u.buf), 0);

For time being we are applying a header trick on OSv side to re-define
MSG_DONTWAIT as 0 when compiling those specific musl sources.


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