This patch sets skb->protocol before transmitting frames on the HDLC device, so that a user listening on the HDLC device with an AF_PACKET socket will see outgoing frames' sll_protocol field correctly set and consistent with that of incoming frames. 1. Control frames in hdlc_cisco and hdlc_ppp When these drivers send control frames, skb->protocol is not set. This value should be set to htons(ETH_P_HDLC), because when receiving control frames, their skb->protocol is set to htons(ETH_P_HDLC). When receiving, hdlc_type_trans in hdlc.h is called, which then calls cisco_type_trans or ppp_type_trans. The skb->protocol of control frames is set to htons(ETH_P_HDLC) so that the control frames can be received by hdlc_rcv in hdlc.c, which calls cisco_rx or ppp_rx to process the control frames. 2. hdlc_fr When this driver sends control frames, skb->protocol is set to internal values used in this driver. When this driver sends data frames (from upper stacked PVC devices), skb->protocol is the same as that of the user data packet being sent on the upper PVC device (for normal PVC devices), or is htons(ETH_P_802_3) (for Ethernet-emulating PVC devices). However, skb->protocol for both control frames and data frames should be set to htons(ETH_P_HDLC), because when receiving, all frames received on the HDLC device will have their skb->protocol set to htons(ETH_P_HDLC). When receiving, hdlc_type_trans in hdlc.h is called, and because this driver doesn't provide a type_trans function in struct hdlc_proto, all frames will have their skb->protocol set to htons(ETH_P_HDLC). The frames are then received by hdlc_rcv in hdlc.c, which calls fr_rx to process the frames (control frames are consumed and data frames are re-received on upper PVC devices). Cc: Krzysztof Halasa <khc@pm.waw.pl> Signed-off-by: Xie He <xie.he.0141@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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Documentation | ||
LICENSES | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.clang-format | ||
.cocciconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
README |
README
Linux kernel ============ There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. The formatted documentation can also be read online at: https://www.kernel.org/doc/html/latest/ There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.