Re: [PATCH 1/4] lwip: Fix bug: Remove unsupported flags when calling send().

[Joan Lledó]

Missatge de Samuel Thibault <samuel.thibault@gnu.org> del dia dj., 2
de maig 2019 a les 23:55:
> Put another way: instead, we have to go through flags which we see
> happen in the wild, and take appropriate measures (which may really be
> to just let lwip_sendmsg return EINVAL, or do the check ourselves if
> lwip_sendmsg does assertions instead of returning EINVAL).

What POSIX[1] says is that here we must return -1 and set errno to
EOPNOTSUPP, and that's what lwip does, so if this patch is not applied
it works fine. But there's a problem: you can't use lwip to resolve
names. In my tests, it seems glibc always add the flag MSG_NOSIGNAL to
the send() call when trying to resolve a name, which is an unsupported
flag. This is a big loss of functionality, what should we do?

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[1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/sendmsg.html