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Date: Mon, 13 Jun 2022 11:41:57 -0400
From: Waldek Kozaczuk <jwkozaczuk@...il.com>
To: musl@...ts.openwall.com
Subject: netlink.c: missing handling of EAGAIN and EWOULDBLOCK
Hi,
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
https://github.com/ifduyue/musl/blob/master/src/network/netlink.c 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.
Waldek
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