[DCCP]: calling dccp_v{4,6}_reqsk_send_ack is a BUG

This patch removes two functions, the send_ack functions of request_sock,
which are not called/used by the DCCP code. It is correct that these
functions are not called, below is a justification why calling these
functions (on a passive socket in the LISTEN/RESPOND state) would mean
a DCCP protocol violation.

A) Background: using request_sock in TCP:

1 files changed, 1 insertions, 47 deletions

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 7107885ada7e..8dd9f5aa27a2 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -193,52 +193,6 @@ static inline void dccp_do_pmtu_discovery(struct sock *sk,
         } /* else let the usual retransmit timer handle it */
 }
 
-static void dccp_v4_reqsk_send_ack(struct sk_buff *rxskb,
-                                   struct request_sock *req)
-{
-        int err;
-        struct dccp_hdr *rxdh = dccp_hdr(rxskb), *dh;
-        const u32 dccp_hdr_ack_len = sizeof(struct dccp_hdr) +
-                                     sizeof(struct dccp_hdr_ext) +
-                                     sizeof(struct dccp_hdr_ack_bits);
-        struct sk_buff *skb;
-
-        if (((struct rtable *)rxskb->dst)->rt_type != RTN_LOCAL)
-                return;
-
-        skb = alloc_skb(dccp_v4_ctl_socket->sk->sk_prot->max_header, GFP_ATOMIC);
-        if (skb == NULL)
-                return;
-
-        /* Reserve space for headers. */
-        skb_reserve(skb, dccp_v4_ctl_socket->sk->sk_prot->max_header);
-        skb->dst = dst_clone(rxskb->dst);
-
-        dh = dccp_zeroed_hdr(skb, dccp_hdr_ack_len);
-
-        /* Build DCCP header and checksum it. */
-        dh->dccph_type     = DCCP_PKT_ACK;
-        dh->dccph_sport    = rxdh->dccph_dport;
-        dh->dccph_dport    = rxdh->dccph_sport;
-        dh->dccph_doff     = dccp_hdr_ack_len / 4;
-        dh->dccph_x        = 1;
-
-        dccp_hdr_set_seq(dh, DCCP_SKB_CB(rxskb)->dccpd_ack_seq);
-        dccp_hdr_set_ack(dccp_hdr_ack_bits(skb),
-                         DCCP_SKB_CB(rxskb)->dccpd_seq);
-
-        bh_lock_sock(dccp_v4_ctl_socket->sk);
-        err = ip_build_and_send_pkt(skb, dccp_v4_ctl_socket->sk,
-                                    rxskb->nh.iph->daddr,
-                                    rxskb->nh.iph->saddr, NULL);
-        bh_unlock_sock(dccp_v4_ctl_socket->sk);
-
-        if (err == NET_XMIT_CN || err == 0) {
-                DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
-                DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
-        }
-}
-
 static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
                                  struct dst_entry *dst)
 {
@@ -1014,7 +968,7 @@ static struct request_sock_ops dccp_request_sock_ops __read_mostly = {
         .family         = PF_INET,
         .obj_size       = sizeof(struct dccp_request_sock),
         .rtx_syn_ack    = dccp_v4_send_response,
-        .send_ack       = dccp_v4_reqsk_send_ack,
+        .send_ack       = dccp_reqsk_send_ack,
         .destructor     = dccp_v4_reqsk_destructor,
         .send_reset     = dccp_v4_ctl_send_reset,
 };