From 6ff509af3869ccac69dcf8905fc75b9a76951594 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= Date: Thu, 18 Apr 2013 12:57:09 +0000 Subject: [PATCH 1/3] net: qmi_wwan: fixup missing ethernet header (firmware bug workaround) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A number of LTE devices from different vendors all suffer from the same firmware bug: Most of the packets received from the device while it is attached to a LTE network will not have an ethernet header. The devices work as expected when attached to 2G or 3G networks, sending an ethernet header with all packets. This driver is not aware of which network the modem attached to, and even if it were there are still some packet types which are always received with the header intact. All devices supported by this driver have severely limited networking capabilities: - can only transmit IPv4, IPv6 and possibly ARP - can only support a single host hardware address at any time - will only do point-to-point communcation with the host Because of this, we are able to reliably identify any bogus raw IP packets by simply looking at the 4 IP version bits. All we need to do is to avoid 4 or 6 in the first digit of the mac address. This workaround ensures this, and fix up the received packets as necessary. Given the distribution of the bug, it is believed that the source is the chipset vendor. The devices which are verified to be affected are: Huawei E392u-12 (Qualcomm MDM9200) Pantech UML290 (Qualcomm MDM9600) Novatel USB551L (Qualcomm MDM9600) Novatel E362 (Qualcomm MDM9600) It is believed that the bug depend on firmware revision, which means that possibly all devices based on the above mentioned chipset may be affected if we consider all available firmware revisions. The information about affected devices and versions is likely incomplete. As the additional overhead for packets not needing this fixup is very small, it is considered acceptable to apply the workaround to all devices handled by this driver. Reported-by: Dan Williams Signed-off-by: Bjørn Mork Signed-off-by: David S. Miller --- drivers/net/usb/qmi_wwan.c | 84 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 84 insertions(+) diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c index 968d5d50751d..d8a50c781af0 100644 --- a/drivers/net/usb/qmi_wwan.c +++ b/drivers/net/usb/qmi_wwan.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -52,6 +53,82 @@ struct qmi_wwan_state { struct usb_interface *data; }; +/* Make up an ethernet header if the packet doesn't have one. + * + * A firmware bug common among several devices cause them to send raw + * IP packets under some circumstances. There is no way for the + * driver/host to know when this will happen. And even when the bug + * hits, some packets will still arrive with an intact header. + * + * The supported devices are only capably of sending IPv4, IPv6 and + * ARP packets on a point-to-point link. Any packet with an ethernet + * header will have either our address or a broadcast/multicast + * address as destination. ARP packets will always have a header. + * + * This means that this function will reliably add the appropriate + * header iff necessary, provided our hardware address does not start + * with 4 or 6. + */ +static int qmi_wwan_rx_fixup(struct usbnet *dev, struct sk_buff *skb) +{ + __be16 proto; + + /* usbnet rx_complete guarantees that skb->len is at least + * hard_header_len, so we can inspect the dest address without + * checking skb->len + */ + switch (skb->data[0] & 0xf0) { + case 0x40: + proto = htons(ETH_P_IP); + break; + case 0x60: + proto = htons(ETH_P_IPV6); + break; + default: + /* pass along other packets without modifications */ + return 1; + } + if (skb_headroom(skb) < ETH_HLEN) + return 0; + skb_push(skb, ETH_HLEN); + skb_reset_mac_header(skb); + eth_hdr(skb)->h_proto = proto; + memset(eth_hdr(skb)->h_source, 0, ETH_ALEN); + memcpy(eth_hdr(skb)->h_dest, dev->net->dev_addr, ETH_ALEN); + return 1; +} + +/* very simplistic detection of IPv4 or IPv6 headers */ +static bool possibly_iphdr(const char *data) +{ + return (data[0] & 0xd0) == 0x40; +} + +/* disallow addresses which may be confused with IP headers */ +static int qmi_wwan_mac_addr(struct net_device *dev, void *p) +{ + int ret; + struct sockaddr *addr = p; + + ret = eth_prepare_mac_addr_change(dev, p); + if (ret < 0) + return ret; + if (possibly_iphdr(addr->sa_data)) + return -EADDRNOTAVAIL; + eth_commit_mac_addr_change(dev, p); + return 0; +} + +static const struct net_device_ops qmi_wwan_netdev_ops = { + .ndo_open = usbnet_open, + .ndo_stop = usbnet_stop, + .ndo_start_xmit = usbnet_start_xmit, + .ndo_tx_timeout = usbnet_tx_timeout, + .ndo_change_mtu = usbnet_change_mtu, + .ndo_set_mac_address = qmi_wwan_mac_addr, + .ndo_validate_addr = eth_validate_addr, +}; + /* using a counter to merge subdriver requests with our own into a combined state */ static int qmi_wwan_manage_power(struct usbnet *dev, int on) { @@ -229,6 +306,12 @@ next_desc: usb_driver_release_interface(driver, info->data); } + /* make MAC addr easily distinguishable from an IP header */ + if (possibly_iphdr(dev->net->dev_addr)) { + dev->net->dev_addr[0] |= 0x02; /* set local assignment bit */ + dev->net->dev_addr[0] &= 0xbf; /* clear "IP" bit */ + } + dev->net->netdev_ops = &qmi_wwan_netdev_ops; err: return status; } @@ -307,6 +390,7 @@ static const struct driver_info qmi_wwan_info = { .bind = qmi_wwan_bind, .unbind = qmi_wwan_unbind, .manage_power = qmi_wwan_manage_power, + .rx_fixup = qmi_wwan_rx_fixup, }; #define HUAWEI_VENDOR_ID 0x12D1 From 6483bdc9d76fb98174797516a19d289eb837909e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= Date: Thu, 18 Apr 2013 12:57:10 +0000 Subject: [PATCH 2/3] net: qmi_wwan: fixup destination address (firmware bug workaround) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Received packets are sometimes addressed to 00:a0:c6:00:00:00 instead of the address the device firmware should have learned from the host: 321.224126 77.16.85.204 -> 148.122.171.134 ICMP 98 Echo (ping) request id=0x4025, seq=64/16384, ttl=64 0000 82 c0 82 c9 f1 67 82 c0 82 c9 f1 67 08 00 45 00 .....g.....g..E. 0010 00 54 00 00 40 00 40 01 57 cc 4d 10 55 cc 94 7a .T..@.@.W.M.U..z 0020 ab 86 08 00 62 fc 40 25 00 40 b2 bc 6e 51 00 00 ....b.@%.@..nQ.. 0030 00 00 6b bd 09 00 00 00 00 00 10 11 12 13 14 15 ..k............. 0040 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 .......... !"#$% 0050 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 &'()*+,-./012345 0060 36 37 67 321.240607 148.122.171.134 -> 77.16.85.204 ICMP 98 Echo (ping) reply id=0x4025, seq=64/16384, ttl=55 0000 00 a0 c6 00 00 00 02 50 f3 00 00 00 08 00 45 00 .......P......E. 0010 00 54 00 56 00 00 37 01 a0 76 94 7a ab 86 4d 10 .T.V..7..v.z..M. 0020 55 cc 00 00 6a fc 40 25 00 40 b2 bc 6e 51 00 00 U...j.@%.@..nQ.. 0030 00 00 6b bd 09 00 00 00 00 00 10 11 12 13 14 15 ..k............. 0040 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 .......... !"#$% 0050 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 &'()*+,-./012345 0060 36 37 67 The bogus address is always the same, and matches the address suggested by many devices as a default address. It is likely a hardcoded firmware default. The circumstances where this bug has been observed indicates that the trigger is related to timing or some other factor the host cannot control. Repeating the exact same configuration sequence that caused it to trigger once, will not necessarily cause it to trigger the next time. Reproducing the bug is therefore difficult. This opens up a possibility that the bug is more common than we can confirm, because affected devices often will work properly again after a reset. A procedure most users are likely to try out before reporting a bug. Unconditionally rewriting the destination address if the first digit of the received packet is 0, is considered an acceptable compromise since we already have to inspect this digit. The simplification will cause unnecessary rewrites if the real address starts with 0, but this is still better than adding additional tests for this particular case. Signed-off-by: Bjørn Mork Signed-off-by: David S. Miller --- drivers/net/usb/qmi_wwan.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c index d8a50c781af0..cff0bbdd9f52 100644 --- a/drivers/net/usb/qmi_wwan.c +++ b/drivers/net/usb/qmi_wwan.c @@ -68,6 +68,10 @@ struct qmi_wwan_state { * This means that this function will reliably add the appropriate * header iff necessary, provided our hardware address does not start * with 4 or 6. + * + * Another common firmware bug results in all packets being addressed + * to 00:a0:c6:00:00:00 despite the host address being different. + * This function will also fixup such packets. */ static int qmi_wwan_rx_fixup(struct usbnet *dev, struct sk_buff *skb) { @@ -84,6 +88,12 @@ static int qmi_wwan_rx_fixup(struct usbnet *dev, struct sk_buff *skb) case 0x60: proto = htons(ETH_P_IPV6); break; + case 0x00: + if (is_multicast_ether_addr(skb->data)) + return 1; + /* possibly bogus destination - rewrite just in case */ + skb_reset_mac_header(skb); + goto fix_dest; default: /* pass along other packets without modifications */ return 1; @@ -94,6 +104,7 @@ static int qmi_wwan_rx_fixup(struct usbnet *dev, struct sk_buff *skb) skb_reset_mac_header(skb); eth_hdr(skb)->h_proto = proto; memset(eth_hdr(skb)->h_source, 0, ETH_ALEN); +fix_dest: memcpy(eth_hdr(skb)->h_dest, dev->net->dev_addr, ETH_ALEN); return 1; } From cc6ba5fdaabea7a7b28de3ba1e0fe54d92232fe5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B8rn=20Mork?= Date: Thu, 18 Apr 2013 12:57:11 +0000 Subject: [PATCH 3/3] net: qmi_wwan: prevent duplicate mac address on link (firmware bug workaround) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit We normally trust and use the CDC functional descriptors provided by a number of devices. But some of these will erroneously list the address reserved for the device end of the link. Attempting to use this on both the device and host side will naturally not work. Work around this bug by ignoring the functional descriptor and assign a random address instead in this case. Signed-off-by: Bjørn Mork Signed-off-by: David S. Miller --- drivers/net/usb/qmi_wwan.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c index cff0bbdd9f52..2a3579f67910 100644 --- a/drivers/net/usb/qmi_wwan.c +++ b/drivers/net/usb/qmi_wwan.c @@ -53,6 +53,9 @@ struct qmi_wwan_state { struct usb_interface *data; }; +/* default ethernet address used by the modem */ +static const u8 default_modem_addr[ETH_ALEN] = {0x02, 0x50, 0xf3}; + /* Make up an ethernet header if the packet doesn't have one. * * A firmware bug common among several devices cause them to send raw @@ -317,6 +320,12 @@ next_desc: usb_driver_release_interface(driver, info->data); } + /* Never use the same address on both ends of the link, even + * if the buggy firmware told us to. + */ + if (!compare_ether_addr(dev->net->dev_addr, default_modem_addr)) + eth_hw_addr_random(dev->net); + /* make MAC addr easily distinguishable from an IP header */ if (possibly_iphdr(dev->net->dev_addr)) { dev->net->dev_addr[0] |= 0x02; /* set local assignment bit */