net/mptcp/options.c:203:3: warning: Assignment of function parameter has no effect outside the function.

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   c2e7554e1b85935d962127efa3c2a76483b0b3b6
commit: 6d0060f600adfddaa43fefb96b6b12643331961e mptcp: Write MPTCP DSS headers to outgoing data packets
compiler: h8300-linux-gcc (GCC) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>


cppcheck possible warnings: (new ones prefixed by >>, may not real problems)

   net/mptcp/options.c:57:4: warning: Assignment of function parameter has no effect outside the function. Did you forget dereferencing it? [uselessAssignmentPtrArg]
      ptr += 8;
      ^
>> net/mptcp/options.c:203:3: warning: Assignment of function parameter has no effect outside the function. [uselessAssignmentArg]
     remaining -= map_size;
     ^
   net/mptcp/options.c:257:2: warning: Assignment of function parameter has no effect outside the function. [uselessAssignmentArg]
    remaining -= opt_size;
    ^

vim +203 net/mptcp/options.c

6d0060f600adfdd Mat Martineau 2020-01-21  177  
6d0060f600adfdd Mat Martineau 2020-01-21  178  static bool mptcp_established_options_dss(struct sock *sk, struct sk_buff *skb,
6d0060f600adfdd Mat Martineau 2020-01-21  179  					  unsigned int *size,
6d0060f600adfdd Mat Martineau 2020-01-21  180  					  unsigned int remaining,
6d0060f600adfdd Mat Martineau 2020-01-21  181  					  struct mptcp_out_options *opts)
6d0060f600adfdd Mat Martineau 2020-01-21  182  {
6d0060f600adfdd Mat Martineau 2020-01-21  183  	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
6d0060f600adfdd Mat Martineau 2020-01-21  184  	unsigned int dss_size = 0;
6d0060f600adfdd Mat Martineau 2020-01-21  185  	struct mptcp_ext *mpext;
6d0060f600adfdd Mat Martineau 2020-01-21  186  	struct mptcp_sock *msk;
6d0060f600adfdd Mat Martineau 2020-01-21  187  	unsigned int ack_size;
6d0060f600adfdd Mat Martineau 2020-01-21  188  	u8 tcp_fin;
6d0060f600adfdd Mat Martineau 2020-01-21  189  
6d0060f600adfdd Mat Martineau 2020-01-21  190  	if (skb) {
6d0060f600adfdd Mat Martineau 2020-01-21  191  		mpext = mptcp_get_ext(skb);
6d0060f600adfdd Mat Martineau 2020-01-21  192  		tcp_fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
6d0060f600adfdd Mat Martineau 2020-01-21  193  	} else {
6d0060f600adfdd Mat Martineau 2020-01-21  194  		mpext = NULL;
6d0060f600adfdd Mat Martineau 2020-01-21  195  		tcp_fin = 0;
6d0060f600adfdd Mat Martineau 2020-01-21  196  	}
6d0060f600adfdd Mat Martineau 2020-01-21  197  
6d0060f600adfdd Mat Martineau 2020-01-21  198  	if (!skb || (mpext && mpext->use_map) || tcp_fin) {
6d0060f600adfdd Mat Martineau 2020-01-21  199  		unsigned int map_size;
6d0060f600adfdd Mat Martineau 2020-01-21  200  
6d0060f600adfdd Mat Martineau 2020-01-21  201  		map_size = TCPOLEN_MPTCP_DSS_BASE + TCPOLEN_MPTCP_DSS_MAP64;
6d0060f600adfdd Mat Martineau 2020-01-21  202  
6d0060f600adfdd Mat Martineau 2020-01-21 @203  		remaining -= map_size;
6d0060f600adfdd Mat Martineau 2020-01-21  204  		dss_size = map_size;
6d0060f600adfdd Mat Martineau 2020-01-21  205  		if (mpext)
6d0060f600adfdd Mat Martineau 2020-01-21  206  			opts->ext_copy = *mpext;
6d0060f600adfdd Mat Martineau 2020-01-21  207  
6d0060f600adfdd Mat Martineau 2020-01-21  208  		if (skb && tcp_fin &&
6d0060f600adfdd Mat Martineau 2020-01-21  209  		    subflow->conn->sk_state != TCP_ESTABLISHED)
6d0060f600adfdd Mat Martineau 2020-01-21  210  			mptcp_write_data_fin(subflow, &opts->ext_copy);
6d0060f600adfdd Mat Martineau 2020-01-21  211  	}
6d0060f600adfdd Mat Martineau 2020-01-21  212  
6d0060f600adfdd Mat Martineau 2020-01-21  213  	ack_size = TCPOLEN_MPTCP_DSS_ACK64;
6d0060f600adfdd Mat Martineau 2020-01-21  214  
6d0060f600adfdd Mat Martineau 2020-01-21  215  	/* Add kind/length/subtype/flag overhead if mapping is not populated */
6d0060f600adfdd Mat Martineau 2020-01-21  216  	if (dss_size == 0)
6d0060f600adfdd Mat Martineau 2020-01-21  217  		ack_size += TCPOLEN_MPTCP_DSS_BASE;
6d0060f600adfdd Mat Martineau 2020-01-21  218  
6d0060f600adfdd Mat Martineau 2020-01-21  219  	dss_size += ack_size;
6d0060f600adfdd Mat Martineau 2020-01-21  220  
6d0060f600adfdd Mat Martineau 2020-01-21  221  	msk = mptcp_sk(mptcp_subflow_ctx(sk)->conn);
6d0060f600adfdd Mat Martineau 2020-01-21  222  	if (msk) {
6d0060f600adfdd Mat Martineau 2020-01-21  223  		opts->ext_copy.data_ack = msk->ack_seq;
6d0060f600adfdd Mat Martineau 2020-01-21  224  	} else {
6d0060f600adfdd Mat Martineau 2020-01-21  225  		mptcp_crypto_key_sha(mptcp_subflow_ctx(sk)->remote_key,
6d0060f600adfdd Mat Martineau 2020-01-21  226  				     NULL, &opts->ext_copy.data_ack);
6d0060f600adfdd Mat Martineau 2020-01-21  227  		opts->ext_copy.data_ack++;
6d0060f600adfdd Mat Martineau 2020-01-21  228  	}
6d0060f600adfdd Mat Martineau 2020-01-21  229  
6d0060f600adfdd Mat Martineau 2020-01-21  230  	opts->ext_copy.ack64 = 1;
6d0060f600adfdd Mat Martineau 2020-01-21  231  	opts->ext_copy.use_ack = 1;
6d0060f600adfdd Mat Martineau 2020-01-21  232  
6d0060f600adfdd Mat Martineau 2020-01-21  233  	*size = ALIGN(dss_size, 4);
6d0060f600adfdd Mat Martineau 2020-01-21  234  	return true;
6d0060f600adfdd Mat Martineau 2020-01-21  235  }
6d0060f600adfdd Mat Martineau 2020-01-21  236  

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