l2tp: add peer_offset parameter

Introduce peer_offset parameter in order to add the capability
to specify two different values for payload offset on tx/rx side.
If just offset is provided by userspace use it for rx side as well
in order to maintain compatibility with older l2tp versions

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 37 insertions, 8 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 115918ad8eca..6ff64717da1e 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -792,7 +792,7 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
                         ptr += 2 + offset;
                 }
         } else
-                ptr += session->offset;
+                ptr += session->peer_offset;
 
         offset = ptr - optr;
         if (!pskb_may_pull(skb, offset))
@@ -1785,6 +1785,7 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
                         session->lns_mode = cfg->lns_mode;
                         session->reorder_timeout = cfg->reorder_timeout;
                         session->offset = cfg->offset;
+                        session->peer_offset = cfg->peer_offset;
                         session->l2specific_type = cfg->l2specific_type;
                         session->l2specific_len = cfg->l2specific_len;
                         session->cookie_len = cfg->cookie_len;
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 9534e16965cc..c6fe7cc42a05 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -59,7 +59,8 @@ struct l2tp_session_cfg {
         int                     debug;          /* bitmask of debug message
                                                  * categories */
         u16                     vlan_id;        /* VLAN pseudowire only */
-        u16                     offset;         /* offset to payload */
+        u16                     offset;         /* offset to tx payload */
+        u16                     peer_offset;    /* offset to rx payload */
         u16                     l2specific_len; /* Layer 2 specific length */
         u16                     l2specific_type; /* Layer 2 specific type */
         u8                      cookie[8];      /* optional cookie */
@@ -86,8 +87,14 @@ struct l2tp_session {
         int                     cookie_len;
         u8                      peer_cookie[8];
         int                     peer_cookie_len;
-        u16                     offset;         /* offset from end of L2TP header
-                                                   to beginning of data */
+        u16                     offset;         /* offset from end of L2TP
+                                                 * header to beginning of
+                                                 * tx data
+                                                 */
+        u16                     peer_offset;    /* offset from end of L2TP
+                                                 * header to beginning of
+                                                 * rx data
+                                                 */
         u16                     l2specific_len;
         u16                     l2specific_type;
         u16                     hdr_len;
diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c
index eb69411bcb47..4cc30b38aba4 100644
--- a/net/l2tp/l2tp_debugfs.c
+++ b/net/l2tp/l2tp_debugfs.c
@@ -180,8 +180,9 @@ static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
                    session->lns_mode ? "LNS" : "LAC",
                    session->debug,
                    jiffies_to_msecs(session->reorder_timeout));
-        seq_printf(m, "   offset %hu l2specific %hu/%hu\n",
-                   session->offset, session->l2specific_type, session->l2specific_len);
+        seq_printf(m, "   offset %hu peer_offset %hu l2specific %hu/%hu\n",
+                   session->offset, session->peer_offset,
+                   session->l2specific_type, session->l2specific_len);
         if (session->cookie_len) {
                 seq_printf(m, "   cookie %02x%02x%02x%02x",
                            session->cookie[0], session->cookie[1],
@@ -228,7 +229,8 @@ static int l2tp_dfs_seq_show(struct seq_file *m, void *v)
                 seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
                 seq_puts(m, "  SESSION ID, peer ID, PWTYPE\n");
                 seq_puts(m, "   refcnt cnt\n");
-                seq_puts(m, "   offset OFFSET l2specific TYPE/LEN\n");
+                seq_puts(m, "   offset OFFSET peer_offset OFFSET");
+                seq_puts(m, " l2specific TYPE/LEN\n");
                 seq_puts(m, "   [ cookie ]\n");
                 seq_puts(m, "   [ peer cookie ]\n");
                 seq_puts(m, "   config mtu/mru/rcvseq/sendseq/dataseq/lns debug reorderto\n");
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 7e9c50125556..d7d4d7a7a54d 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -547,9 +547,25 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
         }
 
         if (tunnel->version > 2) {
-                if (info->attrs[L2TP_ATTR_OFFSET])
+                if (info->attrs[L2TP_ATTR_PEER_OFFSET]) {
+                        struct nlattr *peer_offset;
+
+                        peer_offset = info->attrs[L2TP_ATTR_PEER_OFFSET];
+                        cfg.peer_offset = nla_get_u16(peer_offset);
+                }
+
+                if (info->attrs[L2TP_ATTR_OFFSET]) {
                         cfg.offset = nla_get_u16(info->attrs[L2TP_ATTR_OFFSET]);
 
+                        /* in order to maintain compatibility with older
+                         * versions where offset was used for both tx and
+                         * rx side, update rx side with offset if peer_offset
+                         * is not provided by userspace
+                         */
+                        if (!info->attrs[L2TP_ATTR_PEER_OFFSET])
+                                cfg.peer_offset = cfg.offset;
+                }
+
                 if (info->attrs[L2TP_ATTR_DATA_SEQ])
                         cfg.data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);
 
@@ -763,6 +779,8 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
              nla_put_string(skb, L2TP_ATTR_IFNAME, session->ifname)) ||
             (session->offset &&
              nla_put_u16(skb, L2TP_ATTR_OFFSET, session->offset)) ||
+            (session->peer_offset &&
+             nla_put_u16(skb, L2TP_ATTR_PEER_OFFSET, session->peer_offset)) ||
             (session->cookie_len &&
              nla_put(skb, L2TP_ATTR_COOKIE, session->cookie_len,
                      &session->cookie[0])) ||
@@ -903,6 +921,7 @@ static const struct nla_policy l2tp_nl_policy[L2TP_ATTR_MAX + 1] = {
         [L2TP_ATTR_PW_TYPE]             = { .type = NLA_U16, },
         [L2TP_ATTR_ENCAP_TYPE]          = { .type = NLA_U16, },
         [L2TP_ATTR_OFFSET]              = { .type = NLA_U16, },
+        [L2TP_ATTR_PEER_OFFSET]         = { .type = NLA_U16, },
         [L2TP_ATTR_DATA_SEQ]            = { .type = NLA_U8, },
         [L2TP_ATTR_L2SPEC_TYPE]         = { .type = NLA_U8, },
         [L2TP_ATTR_L2SPEC_LEN]          = { .type = NLA_U8, },