af_packet: fix for sending VLAN frames via packet_mmap

Since tpacket_fill_skb() parses the protocol field in ethernet frames'
headers, it's easy to see if any passed frame is a VLAN one and account
for the extended size.

But as the real protocol does not turn up before tpacket_fill_skb()
runs which in turn also checks the frame length, move the max frame
length calculation into the function.

Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 11 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 71db35ecba39..2b1470de9e16 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -1924,7 +1924,7 @@ 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;
+        int to_write, offset, len, tp_len, nr_frags, len_max, max_frame_len;
         struct socket *sock = po->sk.sk_socket;
         struct page *page;
         void *data;
@@ -1947,10 +1947,6 @@ 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);
@@ -2013,6 +2009,18 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
                 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);
@@ -2051,7 +2059,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
         struct net_device *dev;
         __be16 proto;
         bool need_rls_dev = false;
-        int err, reserve = 0;
+        int err;
         void *ph;
         struct sockaddr_ll *saddr = (struct sockaddr_ll *)msg->msg_name;
         int tp_len, size_max;
@@ -2084,8 +2092,6 @@ 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;
@@ -2093,9 +2099,6 @@ 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);