mptcp: fullmesh: extract RM_ADDR option manipulation

Move these operations -- space check and filling -- to dedicated
functions to be able to re-use them in other path-managers later.

Also, it makes sense to move the manipulation of the TCP Options
elsewhere.

For the new function in mptcp_output.c, symbols have to be exported to
be able to use it from kernel modules as the PMs can be compiled as
modules.

Reviewed-by: Tim Froidcoeur <tim.froidcoeur@tessares.net>
Acked-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
(cherry picked from commit 7c18800)
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>

include/net/mptcp.h

@@ -1385,12 +1385,25 @@ static inline bool mptcp_options_add_addr6_enough_space(const struct mptcp_cb *m
 	return remaining >= MPTCP_SUB_LEN_ADD_ADDR6_ALIGN_VER1;
 }
 
+static inline bool mptcp_options_rm_addr_enough_space(u16 remove_addrs,
+						      int *remove_addr_len,
+						      unsigned int size)
+{
+	unsigned int remaining = MAX_TCP_OPTION_SPACE - size;
+
+	*remove_addr_len = mptcp_sub_len_remove_addr_align(remove_addrs);
+
+	return remaining >= *remove_addr_len;
+}
+
 unsigned int mptcp_options_fill_add_addr4(struct mptcp_cb *mpcb,
 					  struct tcp_out_options *opts,
 					  struct mptcp_loc4 *loc);
 unsigned int mptcp_options_fill_add_addr6(struct mptcp_cb *mpcb,
 					  struct tcp_out_options *opts,
 					  struct mptcp_loc6 *loc);
+unsigned int mptcp_options_fill_rm_addr(struct tcp_out_options *opts,
+					u16 remove_addrs, int remove_addr_len);
 
 /* TCP and MPTCP mpc flag-depending functions */
 u16 mptcp_select_window(struct sock *sk);

net/mptcp/mptcp_fullmesh.c

@@ -1632,14 +1632,13 @@ static void full_mesh_addr_signal(struct sock *sk, unsigned *size,
 	if (likely(!fmp->remove_addrs))
 		goto exit;
 
-	remove_addr_len = mptcp_sub_len_remove_addr_align(fmp->remove_addrs);
-	if (MAX_TCP_OPTION_SPACE - *size < remove_addr_len)
+	if (!mptcp_options_rm_addr_enough_space(fmp->remove_addrs,
+						&remove_addr_len, *size))
 		goto exit;
 
-	opts->options |= OPTION_MPTCP;
-	opts->mptcp_options |= OPTION_REMOVE_ADDR;
-	opts->remove_addrs = fmp->remove_addrs;
-	*size += remove_addr_len;
+	*size += mptcp_options_fill_rm_addr(opts, fmp->remove_addrs,
+					    remove_addr_len);
+
 	if (skb)
 		fmp->remove_addrs = 0;
 

net/mptcp/mptcp_output.c

@@ -2108,3 +2108,14 @@ unsigned int mptcp_options_fill_add_addr6(struct mptcp_cb *mpcb,
 	return MPTCP_SUB_LEN_ADD_ADDR6_ALIGN_VER1;
 }
 EXPORT_SYMBOL(mptcp_options_fill_add_addr6);
+
+unsigned int mptcp_options_fill_rm_addr(struct tcp_out_options *opts,
+					u16 remove_addrs, int remove_addr_len)
+{
+	opts->options |= OPTION_MPTCP;
+	opts->mptcp_options |= OPTION_REMOVE_ADDR;
+	opts->remove_addrs = remove_addrs;
+
+	return remove_addr_len;
+}
+EXPORT_SYMBOL(mptcp_options_fill_rm_addr);