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Libc: MSG_PEEK support

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As discovered by Johannes Kliemann, peeking at buffered socket data
using 'recv' and 'MSG_PEEK' is not supported. Read a "peek" control file
from the socket directory to attempt to peek into buffers at the
socket_fs. Support for every feature of POSIX sockets cannot be
expected, but this one is trivial to implement.

Fix #2875
This commit is contained in:
Emery Hemingway 2018-06-21 09:42:17 +02:00 committed by Norman Feske
parent 7f928a6573
commit adb48b5c9e
1 changed files with 7 additions and 4 deletions
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11
repos/libports/src/lib/libc/socket_fs_plugin.cc
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@ -131,7 +131,7 @@ struct Libc::Socket_fs::Context : Plugin_context
private:
enum Fd : unsigned {
DATA, CONNECT, BIND, LISTEN, ACCEPT, LOCAL, REMOTE, MAX
DATA, PEEK, CONNECT, BIND, LISTEN, ACCEPT, LOCAL, REMOTE, MAX
};
struct
@ -140,7 +140,7 @@ struct Libc::Socket_fs::Context : Plugin_context
int num;
File_descriptor *file;
} _fd[Fd::MAX] = {
{ "data", -1, nullptr },
{ "data", -1, nullptr }, { "peek", -1, nullptr },
{ "connect", -1, nullptr }, { "bind", -1, nullptr },
{ "listen", -1, nullptr }, { "accept", -1, nullptr },
{ "local", -1, nullptr }, { "remote", -1, nullptr }
@ -205,6 +205,7 @@ struct Libc::Socket_fs::Context : Plugin_context
}
int data_fd() { return _fd_for_type(Fd::DATA, O_RDWR); }
int peek_fd() { return _fd_for_type(Fd::PEEK, O_RDONLY); }
int connect_fd() { return _fd_for_type(Fd::CONNECT, O_RDWR); }
int bind_fd() { return _fd_for_type(Fd::BIND, O_WRONLY); }
int listen_fd() { return _fd_for_type(Fd::LISTEN, O_WRONLY); }
@ -751,9 +752,11 @@ static ssize_t do_recvfrom(File_descriptor *fd,
/* TODO ENOTCONN */
/* TODO ECONNREFUSED */
int data_fd = flags & MSG_PEEK ? context->peek_fd() : context->data_fd();
try {
lseek(context->data_fd(), 0, 0);
ssize_t out_len = read(context->data_fd(), buf, len);
lseek(data_fd, 0, 0);
ssize_t out_len = read(data_fd, buf, len);
return out_len;
} catch (Socket_fs::Context::Inaccessible) {
return Errno(EINVAL);