packet: Revert recent header parsing changes.

This reverts commits:

0f75b09c798ed00c30d7d5551b896be883bc2aeb
cbd89acb9eb257ed3b2be867142583fdcf7fdc5b
c483e02614551e44ced3fe6eedda8e36d3277ccc

Amongst other things, it's modifies the SKB header
to pull the ethernet headers off via eth_type_trans()
on the output path which is bogus.

It's causing serious regressions for people.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 24 insertions, 29 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 0c0f6c9a90e7..4cb28a7f639b 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -88,7 +88,6 @@
 #include <linux/virtio_net.h>
 #include <linux/errqueue.h>
 #include <linux/net_tstamp.h>
-#include <linux/if_arp.h>
 
 #ifdef CONFIG_INET
 #include <net/inet_common.h>
@@ -1924,7 +1923,7 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
                 __be16 proto, unsigned char *addr, int hlen)
 {
         union tpacket_uhdr ph;
-        int to_write, offset, len, tp_len, nr_frags, len_max, max_frame_len;
+        int to_write, offset, len, tp_len, nr_frags, len_max;
         struct socket *sock = po->sk.sk_socket;
         struct page *page;
         void *data;
@@ -1947,6 +1946,10 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
                 tp_len = ph.h1->tp_len;
                 break;
         }
+        if (unlikely(tp_len > size_max)) {
+                pr_err("packet size is too long (%d > %d)\n", tp_len, size_max);
+                return -EMSGSIZE;
+        }
 
         skb_reserve(skb, hlen);
         skb_reset_network_header(skb);
@@ -2002,25 +2005,10 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
                 if (unlikely(err))
                         return err;
 
-                if (dev->type == ARPHRD_ETHER)
-                        skb->protocol = eth_type_trans(skb, dev);
-
                 data += dev->hard_header_len;
                 to_write -= dev->hard_header_len;
         }
 
-        max_frame_len = dev->mtu + dev->hard_header_len;
-        if (skb->protocol == htons(ETH_P_8021Q))
-                max_frame_len += VLAN_HLEN;
-
-        if (size_max > max_frame_len)
-                size_max = max_frame_len;
-
-        if (unlikely(tp_len > size_max)) {
-                pr_err("packet size is too long (%d > %d)\n", tp_len, size_max);
-                return -EMSGSIZE;
-        }
-
         offset = offset_in_page(data);
         len_max = PAGE_SIZE - offset;
         len = ((to_write > len_max) ? len_max : to_write);
@@ -2059,7 +2047,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
         struct net_device *dev;
         __be16 proto;
         bool need_rls_dev = false;
-        int err;
+        int err, reserve = 0;
         void *ph;
         struct sockaddr_ll *saddr = (struct sockaddr_ll *)msg->msg_name;
         int tp_len, size_max;
@@ -2092,6 +2080,8 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
         if (unlikely(dev == NULL))
                 goto out;
 
+        reserve = dev->hard_header_len;
+
         err = -ENETDOWN;
         if (unlikely(!(dev->flags & IFF_UP)))
                 goto out_put;
@@ -2099,6 +2089,9 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
         size_max = po->tx_ring.frame_size
                 - (po->tp_hdrlen - sizeof(struct sockaddr_ll));
 
+        if (size_max > dev->mtu + reserve)
+                size_max = dev->mtu + reserve;
+
         do {
                 ph = packet_current_frame(po, &po->tx_ring,
                                 TP_STATUS_SEND_REQUEST);
@@ -2331,20 +2324,22 @@ static int packet_snd(struct socket *sock,
 
         sock_tx_timestamp(sk, &skb_shinfo(skb)->tx_flags);
 
-        if (dev->type == ARPHRD_ETHER) {
-                skb->protocol = eth_type_trans(skb, dev);
-                if (skb->protocol == htons(ETH_P_8021Q))
-                        reserve += VLAN_HLEN;
-        } else {
-                skb->protocol = proto;
-                skb->dev = dev;
-        }
-
         if (!gso_type && (len > dev->mtu + reserve + extra_len)) {
-                err = -EMSGSIZE;
-                goto out_free;
+                /* Earlier code assumed this would be a VLAN pkt,
+                 * double-check this now that we have the actual
+                 * packet in hand.
+                 */
+                struct ethhdr *ehdr;
+                skb_reset_mac_header(skb);
+                ehdr = eth_hdr(skb);
+                if (ehdr->h_proto != htons(ETH_P_8021Q)) {
+                        err = -EMSGSIZE;
+                        goto out_free;
+                }
         }
 
+        skb->protocol = proto;
+        skb->dev = dev;
         skb->priority = sk->sk_priority;
         skb->mark = sk->sk_mark;