packet: parse tpacket header before skb alloc

GSO packet headers must be stored in the linear skb segment.
Move tpacket header parsing before sock_alloc_send_skb. The GSO
follow-on patch will later increase the skb linear argument to
sock_alloc_send_skb if needed for large packets.

The header parsing code does not require an allocated skb, so is
safe to move. Later pass to tpacket_fill_skb the computed data
start and length.

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index b26df32..89377bf 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -2494,14 +2494,13 @@ static int packet_snd_vnet_gso(struct sk_buff *skb,
 }
 
 static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
-               void *frame, struct net_device *dev, int size_max,
+               void *frame, struct net_device *dev, void *data, int tp_len,
                __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, nr_frags, len_max;
        struct socket *sock = po->sk.sk_socket;
        struct page *page;
-       void *data;
        int err;
 
        ph.raw = frame;
@@ -2513,51 +2512,9 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
        sock_tx_timestamp(&po->sk, &skb_shinfo(skb)->tx_flags);
        skb_shinfo(skb)->destructor_arg = ph.raw;
 
-       switch (po->tp_version) {
-       case TPACKET_V2:
-               tp_len = ph.h2->tp_len;
-               break;
-       default:
-               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);
 
-       if (unlikely(po->tp_tx_has_off)) {
-               int off_min, off_max, off;
-               off_min = po->tp_hdrlen - sizeof(struct sockaddr_ll);
-               off_max = po->tx_ring.frame_size - tp_len;
-               if (sock->type == SOCK_DGRAM) {
-                       switch (po->tp_version) {
-                       case TPACKET_V2:
-                               off = ph.h2->tp_net;
-                               break;
-                       default:
-                               off = ph.h1->tp_net;
-                               break;
-                       }
-               } else {
-                       switch (po->tp_version) {
-                       case TPACKET_V2:
-                               off = ph.h2->tp_mac;
-                               break;
-                       default:
-                               off = ph.h1->tp_mac;
-                               break;
-                       }
-               }
-               if (unlikely((off < off_min) || (off_max < off)))
-                       return -EINVAL;
-               data = ph.raw + off;
-       } else {
-               data = ph.raw + po->tp_hdrlen - sizeof(struct sockaddr_ll);
-       }
        to_write = tp_len;
 
        if (sock->type == SOCK_DGRAM) {
@@ -2615,6 +2572,61 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
        return tp_len;
 }
 
+static int tpacket_parse_header(struct packet_sock *po, void *frame,
+                               int size_max, void **data)
+{
+       union tpacket_uhdr ph;
+       int tp_len, off;
+
+       ph.raw = frame;
+
+       switch (po->tp_version) {
+       case TPACKET_V2:
+               tp_len = ph.h2->tp_len;
+               break;
+       default:
+               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;
+       }
+
+       if (unlikely(po->tp_tx_has_off)) {
+               int off_min, off_max;
+
+               off_min = po->tp_hdrlen - sizeof(struct sockaddr_ll);
+               off_max = po->tx_ring.frame_size - tp_len;
+               if (po->sk.sk_type == SOCK_DGRAM) {
+                       switch (po->tp_version) {
+                       case TPACKET_V2:
+                               off = ph.h2->tp_net;
+                               break;
+                       default:
+                               off = ph.h1->tp_net;
+                               break;
+                       }
+               } else {
+                       switch (po->tp_version) {
+                       case TPACKET_V2:
+                               off = ph.h2->tp_mac;
+                               break;
+                       default:
+                               off = ph.h1->tp_mac;
+                               break;
+                       }
+               }
+               if (unlikely((off < off_min) || (off_max < off)))
+                       return -EINVAL;
+       } else {
+               off = po->tp_hdrlen - sizeof(struct sockaddr_ll);
+       }
+
+       *data = frame + off;
+       return tp_len;
+}
+
 static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
 {
        struct sk_buff *skb;
@@ -2626,6 +2638,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
        bool need_wait = !(msg->msg_flags & MSG_DONTWAIT);
        int tp_len, size_max;
        unsigned char *addr;
+       void *data;
        int len_sum = 0;
        int status = TP_STATUS_AVAILABLE;
        int hlen, tlen;
@@ -2673,6 +2686,11 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
                        continue;
                }
 
+               skb = NULL;
+               tp_len = tpacket_parse_header(po, ph, size_max, &data);
+               if (tp_len < 0)
+                       goto tpacket_error;
+
                status = TP_STATUS_SEND_REQUEST;
                hlen = LL_RESERVED_SPACE(dev);
                tlen = dev->needed_tailroom;
@@ -2686,7 +2704,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
                                err = len_sum;
                        goto out_status;
                }
-               tp_len = tpacket_fill_skb(po, skb, ph, dev, size_max, proto,
+               tp_len = tpacket_fill_skb(po, skb, ph, dev, data, tp_len, proto,
                                          addr, hlen);
                if (likely(tp_len >= 0) &&
                    tp_len > dev->mtu + reserve &&
@@ -2694,6 +2712,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
                        tp_len = -EMSGSIZE;
 
                if (unlikely(tp_len < 0)) {
+tpacket_error:
                        if (po->tp_loss) {
                                __packet_set_status(po, ph,
                                                TP_STATUS_AVAILABLE);