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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1775538548; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Gg4529iHncAEaCTY/PX+ysrl8jbN0pCBm9+RUtBBRwc=; b=i2lgC7UrQgtThApwCXXp6wzUDGPYGkhPc6nkMmPduzhc0/20JvEyEOxzLhn9Wu4yXGIElG PPflyC4WyeXx9M89rDo06ao7bDKZ37nWR0X0w/H0/uCcYqh81ZSv0UPezihkc3Mi9PxDwi mqT6wZneLkfPHsu2X2URRaM7X9T5hH4= X-MC-Unique: flpCFxObOweQEstrpIocrA-1 X-Mimecast-MFC-AGG-ID: flpCFxObOweQEstrpIocrA_1775538543 From: Cindy Lu To: lulu@redhat.com, mst@redhat.com, jasowang@redhat.com, zhangckid@gmail.com, lizhijian@fujitsu.com, jmarcin@redhat.com, qemu-devel@nongnu.org Subject: [RFC v4 4/5] chardev/socket: add AF_PACKET inject path Date: Tue, 7 Apr 2026 13:05:51 +0800 Message-ID: <20260407050818.2249570-5-lulu@redhat.com> In-Reply-To: <20260407050818.2249570-1-lulu@redhat.com> References: <20260407050818.2249570-1-lulu@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" Add the AF_PACKET inject write path for socket chardevs. When a socket backend is opened with af-packet-mode=3Dinject, tcp_chr_write() no longer sends the redirector stream framing through QIOChannel. Instead it parses the existing 4-byte length header, accumulates one complete packet, and frame on the AF_PACKET fd. Signed-off-by: Cindy Lu --- chardev/char-socket.c | 148 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 148 insertions(+) diff --git a/chardev/char-socket.c b/chardev/char-socket.c index c710fdb497..45d06fda8f 100644 --- a/chardev/char-socket.c +++ b/chardev/char-socket.c @@ -108,11 +108,159 @@ static void tcp_chr_accept(QIONetListener *listener, static int tcp_chr_read_poll(void *opaque); static void tcp_chr_disconnect_locked(Chardev *chr); =20 +#define TCP_CHARDEV_AF_PACKET_MAX_FRAME_SIZE 65536 + +static bool tcp_chr_uses_af_packet_inject(SocketChardev *s) +{ + return s->is_af_packet && + s->af_packet_mode_set && + s->af_packet_mode =3D=3D CHARDEV_SOCKET_AF_PACKET_MODE_INJECT; +} + +static ssize_t tcp_chr_send_af_packet(SocketChardev *s, + const uint8_t *buf, + size_t len) +{ +#ifdef CONFIG_LINUX + struct iovec iov =3D { + .iov_base =3D (void *)buf, + .iov_len =3D len, + }; + struct msghdr msg =3D { + .msg_iov =3D &iov, + .msg_iovlen =3D 1, + }; + ssize_t ret; + + if (!s->sioc || s->sioc->localAddr.ss_family !=3D AF_PACKET) { + errno =3D ENOTSOCK; + return -1; + } + + do { + ret =3D sendmsg(s->sioc->fd, &msg, 0); + } while (ret < 0 && errno =3D=3D EINTR); + + return ret; +#else + errno =3D EPROTONOSUPPORT; + return -1; +#endif +} + +static bool tcp_chr_af_packet_prepare_send(SocketChardev *s, uint32_t fram= e_len) +{ + if (frame_len > TCP_CHARDEV_AF_PACKET_MAX_FRAME_SIZE) { + errno =3D EMSGSIZE; + return false; + } + + if (frame_len =3D=3D 0) { + s->af_packet_send_len =3D 0; + s->af_packet_send_offset =3D 0; + s->af_packet_send_len_bytes =3D 0; + return true; + } + + if (s->af_packet_send_buf_size < frame_len) { + s->af_packet_send_buf =3D g_realloc(s->af_packet_send_buf, frame_l= en); + s->af_packet_send_buf_size =3D frame_len; + } + + s->af_packet_send_len =3D frame_len; + s->af_packet_send_offset =3D 0; + s->af_packet_send_len_bytes =3D sizeof(s->af_packet_send_len_buf); + return true; +} + +static int tcp_chr_inject_af_packet(Chardev *chr, + SocketChardev *s, + const uint8_t *buf, + int len) +{ + size_t offset =3D 0; + uint32_t frame_len_be; + + while (offset < len) { + size_t copy; + + if (s->af_packet_send_len_bytes < sizeof(s->af_packet_send_len_buf= )) { + copy =3D MIN(sizeof(s->af_packet_send_len_buf) - + s->af_packet_send_len_bytes, + (size_t)len - offset); + memcpy(s->af_packet_send_len_buf + s->af_packet_send_len_bytes, + buf + offset, copy); + s->af_packet_send_len_bytes +=3D copy; + offset +=3D copy; + + if (s->af_packet_send_len_bytes < + sizeof(s->af_packet_send_len_buf)) { + continue; + } + + memcpy(&frame_len_be, s->af_packet_send_len_buf, + sizeof(frame_len_be)); + if (!tcp_chr_af_packet_prepare_send(s, ntohl(frame_len_be))) { + return -1; + } + if (s->af_packet_send_len =3D=3D 0) { + continue; + } + } + + copy =3D MIN(s->af_packet_send_len - s->af_packet_send_offset, + (size_t)len - offset); + memcpy(s->af_packet_send_buf + s->af_packet_send_offset, + buf + offset, copy); + s->af_packet_send_offset +=3D copy; + offset +=3D copy; + + if (s->af_packet_send_offset =3D=3D s->af_packet_send_len) { + ssize_t ret; + + ret =3D tcp_chr_send_af_packet(s, s->af_packet_send_buf, + s->af_packet_send_len); + + if (ret < 0) { + if (errno =3D=3D EAGAIN || errno =3D=3D EWOULDBLOCK) { + return -1; + } + if (tcp_chr_read_poll(chr) <=3D 0) { + trace_chr_socket_poll_err(chr, chr->label); + tcp_chr_disconnect_locked(chr); + } + return -1; + } + + if (ret !=3D (ssize_t)s->af_packet_send_len) { + if (ret >=3D 0) { + errno =3D EIO; + } + if (tcp_chr_read_poll(chr) <=3D 0) { + trace_chr_socket_poll_err(chr, chr->label); + tcp_chr_disconnect_locked(chr); + } + return -1; + } + + s->af_packet_send_len =3D 0; + s->af_packet_send_offset =3D 0; + s->af_packet_send_len_bytes =3D 0; + } + } + + return len; +} + /* Called with chr_write_lock held. */ static int tcp_chr_write(Chardev *chr, const uint8_t *buf, int len) { SocketChardev *s =3D SOCKET_CHARDEV(chr); =20 + if (tcp_chr_uses_af_packet_inject(s)) { + return tcp_chr_inject_af_packet(chr, s, buf, len); + } + if (s->state =3D=3D TCP_CHARDEV_STATE_CONNECTED) { int ret =3D io_channel_send_full(s->ioc, buf, len, s->write_msgfds, --=20 2.52.0