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Workaround for reported recvmsg() ignoring MSG_PEEK.

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This commit is contained in:
Simon Kelley
2020-04-28 14:02:53 +01:00
parent 8baf583a3f
commit 4890bcdea2
1 changed files with 12 additions and 3 deletions
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15
src/dhcp-common.c
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@@ -38,7 +38,7 @@ void dhcp_common_init(void)
ssize_t recv_dhcp_packet(int fd, struct msghdr *msg)
{
ssize_t sz;
ssize_t sz, new_sz;
while (1)
{
@@ -65,9 +65,18 @@ ssize_t recv_dhcp_packet(int fd, struct msghdr *msg)
}
}
while ((sz = recvmsg(fd, msg, 0)) == -1 && errno == EINTR);
while ((new_sz = recvmsg(fd, msg, 0)) == -1 && errno == EINTR);
/* Some kernels seem to ignore MSG_PEEK, and dequeue the packet anyway.
If that happens we get EAGAIN here because the socket is non-blocking.
Use the result of the original testing recvmsg as long as the buffer
was big enough. There's a small race here that may lose the odd packet,
but it's UDP anyway. */
return (msg->msg_flags & MSG_TRUNC) ? -1 : sz;
if (new_sz == -1 && (errno == EWOULDBLOCK || errno == EAGAIN))
new_sz = sz;
return (msg->msg_flags & MSG_TRUNC) ? -1 : new_sz;
}
struct dhcp_netid *run_tag_if(struct dhcp_netid *tags)